Journal articles: 'Ground loops'

1

Bellan, P. M. "Simple system for locating ground loops." Review of Scientific Instruments 78, no. 6 (June 2007): 065104. http://dx.doi.org/10.1063/1.2745242.

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Zhou, Xiang, Ying Ying Ma, and Xiao Feng Liu. "Research on Dual Ground Loop Vehicle Detection System of Intelligent Transportation." Applied Mechanics and Materials 651-653 (September 2014): 491–94. http://dx.doi.org/10.4028/www.scientific.net/amm.651-653.491.

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To against the inadequate of current gateway detection device in parking lots, toll stations and other public places, the paper provides the program of the use of two ground loops to detect and judge the vehicle entrance and exit actions, designs the dual ground loop vehicle detection system correspondingly, and analyzes how the system works. According to the findings, recommendations will be given to the application scope of the system.

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Yin, Changchun, and Ruo Wang. "Power line ground resistance detection using helicopter electromagnetic systems." GEOPHYSICS 80, no. 2 (March 1, 2015): E125—E133. http://dx.doi.org/10.1190/geo2014-0421.1.

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Power line grounding can be a serious concern for the power supply industry. Only a small amount of ground resistance is acceptable because a good electric contact of power line towers with the earth reduces the possibility of the natural hazard associated with lightning. We investigated the possibility of using helicopter-borne electromagnetic (HEM) apparatus to detect the ground resistances of power line towers. Two induction systems were considered: a transmitter-earth-receiver system and a power line loop-earth-receiver system. The transmitter-earth-receiver system built the background signal in the HEM receiver, whereas the power line loop-earth-receiver system produced the signal used for resolving the power line ground resistances. By ignoring the mutual coupling between the two systems, we calculated the induced electromotive forces in the power line loop above which the HEM bird was flown and its two immediate neighbor loops. We replaced other loops along the power line with the Norton-Thevinin equivalence and solved the current flow in the power line loop by the mesh current method. Using the current in the power line loop as induction source, we calculated the electromagnetic responses in the HEM receiver from the power line loop-earth-receiver system. For identification of the poorly grounded towers, we introduced ratios of in-phase and quadrature to signal amplitude and the HEM phase. We evaluated numerical experiments showing that these parameters can well identify power line towers with high ground resistances, and they were insensitive to the flight altitude and direction. Moreover, we also took the catenaries of the power line into consideration so that the elevation differences between towers resulting from rugged mountains could be easily incorporated into the interpretation. We considered vertical coaxial (VCA) and horizontal coplanar (HCP) coil configurations. It was found that the signal for HCP coil has multiple peaks, whereas the VCA coil signal has only a single peak, so we recommend the VCA coil array for power line ground resistance detection. The inversion of synthetic data showed that the power line ground resistances can be resolved from the HEM survey.

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Davis, Aaron, and James Macnae. "Measuring AEM waveforms with a ground loop." GEOPHYSICS 73, no. 6 (November 2008): F213—F222. http://dx.doi.org/10.1190/1.2976791.

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Measuring a transmitter-current waveform provides critical data unavailable for some airborne electromagnetic (AEM) systems yet needed to model AEM data quantitatively. We developed a novel experimental method of measuring an airborne transmitter waveform by monitoring the current induced in a closed, multiturn, insulated ground loop of known inductance [Formula: see text] and resistance [Formula: see text]. The transmitter waveform of five different time-domain systems is deconvolved from the measured ground-loop response when excited by the primary electromagnetic field of the AEM system. In general, our measurements agree well with contractor-described transmitter current waveforms, although crucial differences exist between our deconvolved waveforms and those described in the literature. Using the pulse-per-second feature of a GPS antenna, the ground loop can monitor the frequency drift of a frequency-domain system. The ground loop behaves like a lossy electric-field antenna when the resistance closing the ground loop is too large. This leads to negatives in the response of coincident-loop systems without including induced polarization effects. After observing exponentially decaying, oscillating-current responses in high-resistance ground loops, we model the observed current with an LRC circuit whose resistance and capacitance represent generalized effective antenna and free-space values. Our model predicts responses that closely match the damped oscillations seen in the airborne response during flyover; however, it does not work well on conductive ground.

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Bellina, F., N. Pomaro, and F. Trevisan. "The Ground Loops Detection System in the RFX Machine." Fusion Technology 30, no. 3P2B (December 1996): 1217–21. http://dx.doi.org/10.13182/fst96-a11963114.

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Qu, L., R. Zhang, H. Lee, and H. Kim. "Compact triple‐band ground radiation antenna using two inner rectangular loops enclosed by two outer loops." Electronics Letters 52, no. 10 (May 2016): 790–92. http://dx.doi.org/10.1049/el.2015.3867.

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Shin, Jeong Soo, Jong Woo Park, and Sean Hay Kim. "Measurement and Verification of Integrated Ground Source Heat Pumps on a Shared Ground Loop." Energies 13, no. 7 (April 6, 2020): 1752. http://dx.doi.org/10.3390/en13071752.

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We propose an integrated geothermal system that consists of air-conditioning and hot water service ground source heat pumps, both of which share a ground water loop. The proposed system increases the COP of the service hot water ground source heat pump by recovering the condensation heat of the air-conditioning ground source heat pump as an evaporator heat source for the hot water service ground source heat pump. Eventually this integration expands the scope and capacity of the evaporator source in addition to the underground water of heat exchangers, which also leads to increase the COP of the air-conditioning ground source heat pump. The integrated geothermal heat pump system was installed in a hotel, and then data were measured for a limited period due to the hotel’s ongoing business activities. A TRNSYS simulation model has been developed as a baseline, and the baseline has been calibrated with the measured data. By running one-year simulations, it turns out that the annual electricity use for heating and cooling, and service hot water was reduced by 19.1% in the cooling season, and by 9.6% in the heating season, with respect to the conventional configuration in which the air-conditioning heat pump and hot water service heat pump work individually on their own ground loops.

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Ali Hamed, S. M., and A. A. Osman. "Design Formulas for Broadband Concentric Circular-Loops Antennas." Advanced Electromagnetics 4, no. 1 (June 11, 2015): 45. http://dx.doi.org/10.7716/aem.v4i1.277.

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This paper presents a simple formulas for designing broadband concentric circular-loops antennas (CCLAs). The loop dimensions for widest bandwidth are expressented in terms of the resonance frequency of the driven loop. The analysis addresses both cases CCLAs with and without ground planes. The presented formulas are employed to design multiple CCLAs. For example, a 3-elements CCLA of a maximum radius of 6.34 cm can be designed to operate with a voltage standing wave ratio (VSWR) < 2 over a frequencies band of a fractional bandwidth of 16.9% with a minimum directivity of 3.9 dB. Addionationally, a 4-elements CCLA of maximum radius of 15 cm can be design to operate in the frequency band extending from 825 MHz to 991 MHz (fractional bandwidth of 18.3%) with a VSWR < 2 and directivity higher than 5.2 dB over the entire band. Furthermore, the analysis shows that a 3-elements CCLA backed with a conducting ground plane improves the fractional bandwidth to 19.6% and directivity to 9.15 dB over the band of interest. The analytical results on designed antennas are validated with simulation results obtained by using the AN-SOF antenna simulation software. An excellent agreement is observed between analytical and AN-SOF simulations results.

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9

Durr, V. "Stereotypic leg searching movements in the stick insect: kinematic analysis, behavioural context and simulation." Journal of Experimental Biology 204, no. 9 (May 1, 2001): 1589–604. http://dx.doi.org/10.1242/jeb.204.9.1589.

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Insects are capable of efficient locomotion in a spatially complex environment, such as walking on a forest floor or climbing in a bush. One behavioural mechanism underlying such adaptability is the searching movement that occurs after loss of ground contact. Here, the kinematic sequence of leg searching movements of the stick insect Carausius morosus is analysed. Searching movements are shown to be stereotypic rhythmic movement sequences consisting of several loops. The typical loop structure allows the mean tarsus trajectory to be calculated using a feature-based averaging procedure. Thus, it is possible to describe the common underlying structure of this movement pattern. Phase relationships between joint angles, analysed for searching front legs, indicate a central role for the thorax-coxa joint in searching movements. Accordingly, the stereotyped loop structure of searching differs between front-, middle- and hindlegs, with leg-specific patterns being caused by differing protraction/retraction movements in the thorax-coxa joint. A simple artificial neural network that had originally been devised to generate simple swing movements allows two essential features of empirical searching trajectories to be simulated: (i) cyclic movements and (ii) the smooth transition into a search trajectory as a non-terminated swing movement. It is possible to generate several loops of a middle-leg search, but the precise size and shape of the loops fall short of a real-life approximation. Incorporation of front-leg retraction or hind-leg protraction during searching will also require an extension to the current model. Finally, front-leg searching occurs simultaneously with antennal movements. Also, because leg searching movements are a local behaviour, the legs remaining on the ground continue their stance phase, causing a forward shift of the body, including the searching leg. As a result of this shift, the centre of the searched space is close to the anterior extreme position of the tarsus during walking, representing the location of most likely ground contact according to past experience. Therefore, the behavioural relevance of searching movements arises from the combined actions of several limbs.

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10

O'Brien, D. M., and R. S. Smith. "Transient electromagnetic response of a layered conducting medium at asymptotically late times." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 27, no. 1 (July 1985): 1–30. http://dx.doi.org/10.1017/s0334270000004732.

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AbstractIn this paper we consider a pair of horizontal conducting loops in the air above a horizontally layered ground. The transmitting loop is driven by a current source which rises from zero at time zero to a final constant value at time τ. We first compute the e.m.f. induced in the receiving loop and derive an asymptotic series for the e.m.f. at late times. Secondly, we estimate the error in truncating the asymptotic series at N terms and design a reliable numerical algorithm for summing the asymptotic series.

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Wang, Xuli, Jing Ma, Feng Zhao, Liang Tang, and Lei Wang. "The modeling and energy efficiency analysis of thermal energy management operation of ground source heat pump air-conditioning system." Thermal Science 24, no. 5 Part B (2020): 3229–37. http://dx.doi.org/10.2298/tsci191123114w.

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To improve the energy-saving effect of the ground source heat pump air-conditioning system, an example is investigated, and the annual loads of the building are simulated and analyzed. The thermal energy management operation modelling is conducted. The hydraulic analysis is performed for different modes in each section. Given the same flow and tube type, a larger pipe diameter indicates a smaller hydraulic loss. Compared with the parallel 5-well loop and the parallel 10-well loop, the hydraulic loss of the series 2-well loop is the highest. When the sub-catch is connected to 5 loops, as the number of series wells increases, the tube length gets longer, the flow rate allocated by the loop gets less, and the load increases. Besides, the energy efficiency ratio of the ground source side decreases as the heat rejection load increases. Therefore, by adjusting the pipe diameter, the pipe type, and the depth of the well, the hydraulic loss can be reduced. The energy-saving effect of the loop in the parallel mode is better. Given the limited number of the managed wells, the parallel circuit can be adjusted to the same program. The connection allows the collector to distribute the flow evenly. The energy efficiency ratio of the ground source can be improved by changing the diameter of the horizontal trunk pipe. It is hoped that the hydraulic optimization design of the ground source heat pump air-conditioning system can provide a theoretical basis for the application and promotion of the ground source heat pumps.

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Mark, Robert, Nipun Mishra, Kaushik Mandal, Partha Pratim Sarkar, and Soma Das. "Hexagonal Nested Loop Fractal Antenna for Quad Band Wireless Applications." Frequenz 73, no. 3-4 (February 25, 2019): 99–108. http://dx.doi.org/10.1515/freq-2018-0115.

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Abstract A compact hexagonal nested loop fractal antenna with L shaped slot on the ground plane is presented for multiband applications. In this paper, the effect of fractal iterations and position of L-slot on ground plane are optimized for better performance of the antenna. Multiple hexagon loops excite multiple resonant modes at 1.7, 2.4, 3.1, 4.5 and 6 GHz and an L-shaped slot on the ground plane helps to achieve wide bandwidth response with better impedance matching in the 4.25–6.41 GHz frequency band. An equivalent circuit of the proposed antenna is modelled and the same is verified using ADS. Reflection coefficient and radiation pattern are presented to further confirm the performance of the proposed design for wireless applications. The proposed antenna is fabricated on a low-cost FR4 substrate of dimensions 40×32×1.6 mm3 and measured results show good agreement with simulation results.

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Jain, Abhinandan, Calvin Kuo, Paramsothy Jayakumar, and Jonathan Cameron. "Constraint Embedding for Vehicle Suspension Dynamics." Archive of Mechanical Engineering 63, no. 2 (June 1, 2016): 193–213. http://dx.doi.org/10.1515/meceng-2016-0011.

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Abstract The goal of this research is to achieve close to real-time dynamics performance for allowing auto-pilot in-the-loop testing of unmanned ground vehicles (UGV) for urban as well as off-road scenarios. The overall vehicle dynamics performance is governed by the multibody dynamics model for the vehicle, the wheel/terrain interaction dynamics and the onboard control system. The topic of this paper is the development of computationally efficient and accurate dynamics model for ground vehicles with complex suspension dynamics. A challenge is that typical vehicle suspensions involve closed-chain loops which require expensive DAE integration techniques. In this paper, we illustrate the use the alternative constraint embedding technique to reduce the cost and improve the accuracy of the dynamics model for the vehicle.

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Charalambous, Maria, Eleni E. Moushi, Constantina Papatriantafyllopoulou, Wolfgang Wernsdorfer, Vassilios Nastopoulos, George Christou, and Anastasios J. Tasiopoulos. "A Mn36Ni4 ‘loop-of-loops-and-supertetrahedra’ aggregate possessing a high ST = 26 ± 1 spin ground state." Chemical Communications 48, no. 44 (2012): 5410. http://dx.doi.org/10.1039/c2cc30654a.

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Shi, Di, Zhong Wu, and Wusheng Chou. "Anti-disturbance trajectory tracking of quadrotor vehicles via generalized extended state observer." Journal of Vibration and Control 26, no. 13-14 (December 30, 2019): 1173–86. http://dx.doi.org/10.1177/1077546319892752.

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During the trajectory tracking process and low altitude flight of quadrotor, wind gust and ground effect will significantly affect the accuracy and stability of the controller. Therefore, it is vital for a quadrotor to have a robust controller against multiple disturbances. To mitigate this challenge, an active anti-disturbance control strategy based on generalized extended state observer is proposed in this article. Firstly, quadrotor dynamics is modeled as cascaded translational and rotational loops, and the characteristics of wind gust and ground effect are analyzed. Secondly, two generalized extended state observers are constructed for those loops respectively to estimate and attenuate the impact of wind gust and ground effect, and the position and attitude controller are designed based on backstepping method. Finally, real time experiments are carried out on hovering and circle trajectory tracking conditions. The results illustrate that the proposed controller has more advantages in high precision trajectory tracking and low altitude flight of quadrotor in existence of multiple disturbances.

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Anand, A., and S. V. Bhat. "Stable ground states for Δϕ=π in double Josephson junction superconducting loops." Physica C: Superconductivity 341-348 (November 2000): 1671–72. http://dx.doi.org/10.1016/s0921-4534(00)00929-1.

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HOSONO, SHINOBU, and SHO TSUJIMARU. "GENERAL CONSTRUCTION OF PHYSICAL STATES IN 2D QUANTUM GRAVITY." International Journal of Modern Physics A 08, no. 26 (October 20, 1993): 4627–48. http://dx.doi.org/10.1142/s0217751x93001855.

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The BRST cohomology of two-dimensional gravity coupled to 0≤c<1 minimal conformal matter is investigated in the conformal gauge. We formulate a general procedure to write down the physical states via the technique of spectral sequences. Paying attention to the ghost sectors, we show that the physical states correspond to the microscopic loops, and the macroscopic loops are described by b-ghosts and c-ghosts respectively. For pure gravity, several physical states are first calculated explicitly and, in addition, the general formula for macroscopic loops is obtained by relating it to a simpler Lie algebra cohomology. We also discuss the local operator algebras of microscopic loops in Liouville theory, the so-called ground ring, in the relation to those from the Schwinger-Dyson equation in the matrix model.

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Alexandrou, Constantia, Martha Constantinou, Kyriakos Hadjiyiannakou, Karl Jansen, Christos Kallidonis, Giannis Koutsou, and Alejandro Vaquero Avilés-Casco. "Connected and disconnected contributions to nucleon axial form factors using Nf = 2 twisted mass fermions at the physical point." EPJ Web of Conferences 175 (2018): 06003. http://dx.doi.org/10.1051/epjconf/201817506003.

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We present results on the isovector and isoscalar nucleon axial form factors including disconnected contributions, using an ensemble of Nf = 2 twisted mass cloverimproved Wilson fermions simulated with approximately the physical value of the pion mass. The light disconnected quark loops are computed using exact deflation, while the strange and the charm quark loops are evaluated using the truncated solver method. Techniques such as the summation and the two-state fits have been employed to access ground-state dominance.

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Zhou, Fangyuan, Weilin Xiang, Kun Ye, and Hongping Zhu. "Theoretical study of the double concave friction pendulum system under variable vertical loading." Advances in Structural Engineering 22, no. 8 (February 19, 2019): 1998–2005. http://dx.doi.org/10.1177/1369433219831474.

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The double concave friction pendulum system has been recognized as an efficient device for decreasing the seismic response of a structure during an earthquake excitation. Previous studies have focused mainly on the properties of the double concave friction pendulum system under constant vertical loading, and the width of the hysteretic loop changed by the vertical ground motion is less considered. In view of this, a theoretical study of the double concave friction pendulum system under variable vertical loading is conducted in this article. Meanwhile, the properties of the hysteretic loops of the double concave friction pendulum system with different friction coefficients between the articulated slider with the upper and lower sliding surfaces are investigated. The results show that the hysteretic loops of the double concave friction pendulum system will be affected by the variation of the vertical loading and the difference of the friction coefficients between the articulated slider with the upper and lower sliding surfaces.

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Oh, Hyunjun, and James M. Tinjum. "Simplified two-step, cross-sectional approach for coupled heat and moisture transfer modeling of shallow, horizontal, ground-based heat Exchangers." E3S Web of Conferences 205 (2020): 07004. http://dx.doi.org/10.1051/e3sconf/202020507004.

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This study evaluates a two-step, cross-sectional approach for designing shallow, unsaturated, horizontal, ground-based heat exchangers (GHXs). Numerical modeling was conducted for coupled heat and moisture transfer around GHXs under transient climatological conditions through a cooling season. Soil samples were collected in Texas and Wisconsin to measure thermal conductivity dry-out curves and soil-water characteristic curves for use in the modeling. Average daily meteorological data from central Texas was applied for the top boundary condition. Heat generation from the GHX was calculated by total condenser heat rejection from an environmental control unit based on ambient temperatures and unit specifications. In the first step of the modeling, results showed that the fluid temperature through the GHX loop was approximately 43 ºC, and rapid heat and moisture fluxes were observed around the GHX loops. High moisture flux along the upper surface was also observed due to high ambient temperatures that occur during the summer season. Using these results, exiting temperature of the GHX was estimated for the second cross-sectional modeling step. This two-step, cross-sectional modeling approach provides a systematic analysis of coupled heat and moisture transfer around shallow, horizontal, unsaturated GHX loops, thus simplifying high computational effort needed for full three-dimensional modeling of shallow GHX systems.

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Liu, Y., and H. Zhang. "Magnetic Configuration and Evolution in a Solar Active Region." Symposium - International Astronomical Union 203 (2001): 294–96. http://dx.doi.org/10.1017/s0074180900219347.

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We present results of the analysis of NOAA 8668, which was observed successively by space satellite (SOHO) and ground-based observatories (BBSO, Huairou). The combined observation offers us a good example of a region observed from low to high solar atmosphere. Several flares and a sigmoid filament were observed in the AR, and we observed the sigmoid filament from its birth to disintegration. The configuration of the magnetic field of the AR changed quickly as well as the loops. From EIT movies, we can even judge the sign of the sigmoid filament's magnetic helicity. The forming and heating of the loops were the result of magnetic reconnection, and the corona seemed heated when the loops became opened.

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Carlozzi, Pietro. "Closed Photobioreactor Assessments to Grow, Intensively, Light Dependent Microorganisms: A Twenty-Year Italian Outdoor Investigation." Open Biotechnology Journal 2, no. 1 (March 4, 2008): 63–72. http://dx.doi.org/10.2174/1874070700802010063.

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Twenty years of Italian outdoor investigations on closed photobioreactors are discussed in this review. Many photobioreactor designs have been projected; some have been built, tested and patented. The Italian research approach from tubular (single tube and traditional loop) to flat and column and again to tubular photobioreactors (coil and loops) has improved microalgal yield. It increased from 25.0 gm-2d-1 in 1986 (using a traditional loop set down on the ground) to 47.7 gm-2d-1 in 2003, when results of a new tubular undulating row photobioreactor (TURP) were reported. This very high TURP productivity was attributed to a light dilution growth-strategy using Arthrospira platensis; the photic ratio (Rf) ranged from 3 to 6.

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Feng, Guirong, Lei Chen, and Xiaowei Shi. "A broadband circularly polarized monopole antenna employing parasitic loops and defective ground plane." Microwave and Optical Technology Letters 62, no. 1 (August 23, 2019): 251–56. http://dx.doi.org/10.1002/mop.31998.

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Zhihua, Z., Y. Jiansheng, and M. Weiming. "Coupling Model and Impedance Calculation of the Steel Ground Loops With Proximity Effect." IEEE Transactions on Electromagnetic Compatibility 48, no. 3 (August 2006): 522–29. http://dx.doi.org/10.1109/temc.2006.877780.

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APAJA, VESA, and OLAV F. SYLJUÅSEN. "MONTE CARLO SIMULATION OF BOSON LATTICES." International Journal of Modern Physics B 20, no. 30n31 (December 20, 2006): 5113–16. http://dx.doi.org/10.1142/s0217979206036168.

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Boson lattices are theoretically well described by the Hubbard model. The basic model and its variants can be effectively simulated using Monte Carlo techniques. We describe two newly developed approaches, the Stochastic Series Expansion (SSE) with directed loop updates and continuous–time Diffusion Monte Carlo (CTDMC). SSE is a formulation of the finite temperature partition function as a stochastic sampling over product terms. Directed loops is a general framework to implement this stochastic sampling in a non–local fashion while maintaining detailed balance. CTDMC is well suited to finding exact ground–state properties, applicable to any lattice model not suffering from the sign problem; for a lattice model the evolution of the wave function can be performed in continuous time without any time discretization error. Both the directed loop algorithm and the CTDMC are important recent advances in development of computational methods. Here we present results for a Hubbard model for anti–ferromagnetic spin–1 bosons in one dimensions, and show evidence for a dimerized ground state in the lowest Mott lobe.

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Bischer, Ingolf, Thierry Grandou, and Ralf Hofmann. "Massive loops in thermal SU(2) Yang–Mills theory: Radiative corrections to the pressure beyond two loops." International Journal of Modern Physics A 32, no. 19n20 (July 12, 2017): 1750118. http://dx.doi.org/10.1142/s0217751x17501184.

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We address the loop expansion of the pressure in the deconfining phase of SU(2) Yang–Mills thermodynamics. We devise an efficient book-keeping of excluded energy-sign and scattering-channel combinations for the loop four-momenta associated with massive quasiparticles, circulating in (connected) bubble diagrams subject to vertex constraints inherited from the thermal ground state. These radiative corrections modify the one-loop pressure exerted by free thermal quasiparticles. Increasing the loop order in two-particle irreducible (2PI) bubble diagrams, we exemplarily demonstrate a suppressing effect of the vertex constraints on the number of valid combinations. This increasingly strong suppression gave rise to the conjecture in arXiv:hep-th/0609033 that the loop expansion would terminate at a finite order. Albeit the low-temperature dependence of the 2PI 3-loop diagram complies with this behavior, a thorough analysis of the high-temperature situation reveals that the leading power in temperature is thirteen such that this diagram dominates all lower loop orders for sufficiently high temperatures. An all-loop-order resummation of 2PI diagrams with dihedral symmetry is thus required, defining an extremely well-bounded analytical continuation of the low-temperature result.

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Cvetkovic, Zlata, Bojana Petkovic, and Mirjana Peric. "An external body in protected area." Facta universitatis - series: Electronics and Energetics 22, no. 2 (2009): 209–15. http://dx.doi.org/10.2298/fuee0902209c.

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In practice, often there is a need for modeling systems for canceling the Earth electrostatic field. For this purpose, a linear circular loop can be used. The realized protection is as better as the used ring is thicker. In practical applications, a system of coaxial linear loops is used instead of one thick ring. In order to find the influence of protected object shape and volume to the electrostatic protection efficiency, a protected object is modeled as a half spherical electrode, placed with its flat side on the ground. According to the theoretical analysis, a general numerical program has been developed and numerical results are shown graphically. .

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Reitstetter, Raven, and Rittenhouse Larry R. "Cheatgrass Invasion - The Below-Ground Connection." Journal of Environment and Ecology 8, no. 1 (May 22, 2017): 27. http://dx.doi.org/10.5296/jee.v8i1.10536.

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Plant-soil microbial feedback loops play an important role in the establishment and development of plant communities. Microbial soil communities, including pathogens, plant-growth-promoting rhizobacteria and their reciprocal interactions, can influence plant health and nutrient cycling in many ways. We are proposing a model that accounts for cheatgrass (Bromus tectorum) invasion success and long-term persistence in both disturbed and undisturbed sites. In this model cheatgrass alters soil microbial communities that favor nitrifying microorganisms, resulting in elevated NO3- levels. Increased NO3- levels, coupled with B. tectorum life history and climatic and edaphic conditions in the semi-arid western U.S., result in long-term persistence of this invasive annual. In ecosystems that lack major precipitation during the growth season, B. tectorum induced shifts in the nitrifier community result in accumulation of plant available nitrogen during the summer when native perennials are primarily dormant. Increased NO3- levels can be efficiently utilized by cheatgrass ahead of native perennials during fall and winter. Restoration and management efforts must be guided by a thorough understanding of soil microbe-cheatgrass interactions to avoid nutrient flushes resulting from freeze-thaw and wet-dry cycles that benefit this invasive grass.

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Lang, K. R. "Very Large Array Observations of Large-Scale Coronal Structures." International Astronomical Union Colloquium 144 (1994): 195–99. http://dx.doi.org/10.1017/s0252921100025306.

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AbstractVery Large Array (VLA) observations indicate that electrons accelerated in one active region can travel along otherwise-invisible, large-scale coronal loops to trigger flares in another widely-separated active region, as well as from the magnetic loops connecting them. The VLA provides high-resolution, full-disk images of quiescent, or non-flaring, coronal loops within individual active regions (at 20 cm) and between or beyond them (at 90 cm). Both ground-based radio telescopes and spaceborne X-ray telescopes provide high-resolution images of the ubiquitous coronal loops whose hot, dense magnetically-trapped plasma emits thermal bremsstrahlung. Radio observations can be used to specify the strength and structure of the magnetic fields in the low solar corona. We find a high magnetic field strength in the million-degree plasma above large sunspots – 75 to 80 percent of the value in the underlying photospheric sunspots; as well as coronal regions of non-potential, current-amplified magnetic fields. Some long-lasting (hours) coronal radio sources found on the Sun and other active stars require nonthermal radiation and nearly continuous acceleration of energetic electrons.

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Romero, A. H., and J. Mejía-López. "Ground state geometries and hysteresis loops of small granular ferrofluids as function of coating." Physica B: Condensed Matter 384, no. 1-2 (October 2006): 244–48. http://dx.doi.org/10.1016/j.physb.2006.06.001.

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Nguyen, Bao Ngoc, Nghiem Xuan Tran, Jin-Tae Han, and Sung-Ruyl Kim. "Evaluation of the dynamic p–yp loops of pile-supported structures on sloping ground." Bulletin of Earthquake Engineering 16, no. 12 (July 27, 2018): 5821–42. http://dx.doi.org/10.1007/s10518-018-0428-3.

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Tanaka, Kanji. "Deformable Map Matching to Handle Uncertain Loop-Less Maps." Journal of Advanced Computational Intelligence and Intelligent Informatics 22, no. 6 (October 20, 2018): 915–23. http://dx.doi.org/10.20965/jaciii.2018.p0915.

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In the classical context of map relative localization, map-matching (MM) is typically defined as the task of finding a rigid transformation (i.e., 3DOF rotation/translation on the 2D moving plane) that aligns two maps, the query and reference maps built by mobile robots. This definition is valid in loop-rich trajectories that enable a mapper robot to close many loops, for which precise maps can be assumed. The same cannot be said about the newly emerging vision only autonomous navigation systems, which typically operate in loop-less trajectories that have no loop (e.g., straight paths). In this paper, we address this limitation by merging the two maps. Our study is motivated by the observation that even when there is no loop in either the query or reference map, many loops can often be obtained in the merged map. We add two new aspects to MM: (1) map retrieval with compact and discriminative binary features powered by deep convolutional neural network (DCNN), which efficiently generates a small number of good initial alignment hypotheses; and (2) map merge, which jointly deforms the two maps to minimize differences in shape between them. A preemption scheme is introduced to avoid excessive evaluation of useless MM hypotheses. For experimental investigation, we created a novel collection of uncertain loop-less maps by utilizing the recently published North Campus Long-Term (NCLT) dataset and its ground-truth GPS data. The results obtained using these map collections confirm that our approach improves on previous MM approaches.

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Asselmeyer-Maluga, Torsten. "Quantum computing and the brain: quantum nets, dessins d’enfants and neural networks." EPJ Web of Conferences 198 (2019): 00014. http://dx.doi.org/10.1051/epjconf/201919800014.

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In this paper, we will discuss a formal link between neural networks and quantum computing. For that purpose we will present a simple model for the description of the neural network by forming sub-graphs of the whole network with the same or a similar state. We will describe the interaction between these areas by closed loops, the feedback loops. The change of the graph is given by the deformations of the loops. This fact can be mathematically formalized by the fundamental group of the graph. Furthermore the neuron has two basic states |0〉 (ground state) and |1〉 (excited state). The whole state of an area of neurons is the linear combination of the two basic state with complex coefficients representing the signals (with 3 Parameters: amplitude, frequency and phase) along the neurons. If something changed in this area, we need a transformation which will preserve this general form of a state (mathematically, this transformation must be an element of the group S L(2; C)). The same argumentation must be true for the feedback loops, i.e. a general transformation of states along the feedback loops is an assignment of this loop to an element of the transformation group. Then it can be shown that the set of all signals forms a manifold (character variety) and all properties of the network must be encoded in this manifold. In the paper, we will discuss how to interpret learning and intuition in this model. Using the Morgan-Shalen compactification, the limit for signals with large amplitude can be analyzed by using quasi-Fuchsian groups as represented by dessins d’enfants (graphs to analyze Riemannian surfaces). As shown by Planat and collaborators, these dessins d’enfants are a direct bridge to (topological) quantum computing with permutation groups. The normalization of the signal reduces to the group S U(2) and the whole model to a quantum network. Then we have a direct connection to quantum circuits. This network can be transformed into operations on tensor networks. Formally we will obtain a link between machine learning and Quantum computing.

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Habibzadeh-Bigdarvish, Omid, Xinbao Yu, and Anand J. Puppala. "Externally heated geothermal bridge deck: Performance analysis of the U-tube ground heat exchanger." E3S Web of Conferences 205 (2020): 07006. http://dx.doi.org/10.1051/e3sconf/202020507006.

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In recent years, the geothermal heat pump de-icing system (GHDS) is introduced as a sustainable solution for bridge deck de-icing, which utilizes renewable geothermal energy. Existing GHDS designs mostly rely upon hydronic loops embedded in concrete decks. To extend the GHDS for existing bridges, a new external hydronic deck has been developed recently, which employs a hydronic pipe being attached to the bottom surface of the bridge deck. In this study, the performance of the externally heated geothermal bridge deck is investigated through winter deicing and summer recharging tests with the focus on the ground loop heat exchanger (GLHE), a key component of the GHDS. The test results show that the de-icing system was successful in maintaining the deck surface temperature above freezing in all winter tests. The soil temperature measurements indicate, the 132.5 m vertical U-tube ground heat exchanger is benefited from the undisturbed soil temperature of around 21 °C. The overall average hourly heat extraction of 0.67 kW during winter operation and average hourly heat injection of 0.69 kW during the summer operation were observed. Also, the ground thermal recharge test showed the increase of undisturbed soil temperature at 1.5 m from the geothermal borehole by 0.36 °C after 50 days of system operation.

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Chae, M. K., Y. Kim, A. Johner, and N. K. Lee. "Adsorption of a Helical Filament Subject to Thermal Fluctuations." Polymers 12, no. 1 (January 10, 2020): 192. http://dx.doi.org/10.3390/polym12010192.

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We consider semiflexible chains governed by preferred curvature and twist and their flexural and twist moduli. These filaments possess a helical rather than straight three-dimensional (3D) ground state and we call them helical filaments (H-filament). Depending on the moduli, the helical shape may be smeared by thermal fluctuations. Secondary superhelical structures are expected to form on top of the specific local structure of biofilaments, as is documented for vimentin. We study confinement and adsorption of helical filaments utilizing both a combination of numerical simulations and analytical theory. We investigate overall chain shapes, transverse chain fluctuations, loop and tail distributions, and energy distributions along the chain together with the mean square average height of the monomers ⟨ z 2 ⟩ . The number fraction of adsorbed monomers serves as an order parameter for adsorption. Signatures of adsorbed helical polymers are the occurrence of 3D helical loops/tails and spiral or wavy quasi-flat shapes. None of these arise for the Worm-Like-Chain, whose straight ground state can be embedded in a plane.

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Muzi, Marco. "AN EXACT EXPRESSION FOR THE MUTUAL IMPEDANCE BETWEEN COAXIAL CIRCULAR LOOPS ON A HOMOGENEOUS GROUND." Progress In Electromagnetics Research Letters 81 (2019): 65–70. http://dx.doi.org/10.2528/pierl18110902.

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Kurtz, Courtney C., Susanne L. Lindell, Martin J. Mangino, and Hannah V. Carey. "Hibernation confers resistance to intestinal ischemia-reperfusion injury." American Journal of Physiology-Gastrointestinal and Liver Physiology 291, no. 5 (November 2006): G895—G901. http://dx.doi.org/10.1152/ajpgi.00155.2006.

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The damaging effects of intestinal ischemia-reperfusion (I/R) on the gut and remote organs can be attenuated by subjecting the intestine to a prior, less severe I/R insult, a process known as preconditioning. Because intestines of hibernating ground squirrels experience repeated cycles of hypoperfusion and reperfusion, we examined whether hibernation serves as a model for natural preconditioning against I/R-induced injury. We induced intestinal I/R in either the entire gut or in isolated intestinal loops using rats, summer ground squirrels, and hibernating squirrels during natural interbout arousals (IBA; body temperature 37–39°C). In both models, I/R induced less mucosal damage in IBA squirrels than in summer squirrels or rats. Superior mesenteric artery I/R increased MPO activity in the gut mucosa and lung of rats and summer squirrels and the liver of rats but had no effect in IBA squirrels. I/R in isolated loops increased luminal albumin levels, suggesting increased gut permeability in rats and summer squirrels but not IBA squirrels. The results suggest that the hibernation phenotype is associated with natural protection against intestinal I/R injury.

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Ringler, Adam T., and Patrick Bastien. "A Brief Introduction to Seismic Instrumentation: Where Does My Data Come From?" Seismological Research Letters 91, no. 2A (January 29, 2020): 1074–83. http://dx.doi.org/10.1785/0220190214.

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Abstract Modern seismology has been able to take advantage of several technological advances. These include feedback loops in the seismometer, specialized digitizers with absolute timing, and compression formats for storing data. While all of these advances have helped improve the field, they can also leave newcomers a bit confused. Our goal here is to give a brief overview of how recordings of seismic ground motion originate. We discuss the chain of events that are required to obtain digital data plus how these steps can be reversed to recover units of ground motion such as acceleration, velocity, or displacement. Finally, we show a few examples of data that have become compromised because of various non-ground-motion signals. We hope this brief overview provides a quick practical introduction to allow the reader to become familiar with the various jargon used in observational seismology.

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Shesterikov, I., K. Crombe, R. Ochoukov, A. Kostic, M. Usoltceva, and J. M. Noterdaeme. "The source of and a simple way to avoid ground loops in biasing Langmuir probe array." Journal of Instrumentation 14, no. 01 (January 3, 2019): P01002. http://dx.doi.org/10.1088/1748-0221/14/01/p01002.

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Sahdane, T., R. Masrour, and A. Jabar. "Ground state phase diagrams and ferroelectric hysteresis loops behaviour of dendrimer superlattice: a Monte Carlo study." Philosophical Magazine 100, no. 22 (July 27, 2020): 2876–88. http://dx.doi.org/10.1080/14786435.2020.1797203.

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41

Johnston, Ian. "Geothermal energy: shallow sources." Proceedings of the Royal Society of Victoria 126, no. 2 (2014): 25. http://dx.doi.org/10.1071/rs14025.

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Below a depth of around 5 to 8 metres below the surface, the ground displays a temperature which is effectively constant and a degree or two above the weighted mean annual air temperature at that particular location. In Melbourne, the ground temperature at this depth is around 18°C with temperatures at shallower depths varying according the season. Further north, these constant temperatures increase a little; while for more southern latitudes, the temperatures are a few degrees cooler. Shallow source geothermal energy (also referred to as direct geothermal energy, ground energy using ground source heat pumps and geoexchange) uses the ground and its temperatures to depths of a few tens of metres as a heat source in winter and a heat sink in summer for heating and cooling buildings. Fluid (usually water) is circulated through a ground heat exchanger (or GHE, which comprises pipes built into building foundations, or in specifically drilled boreholes or trenches), and back to the surface. In heating mode, heat contained in the circulating fluid is extracted by a ground source heat pump (GSHP) and used to heat the building. The cooled fluid is reinjected into the ground loops to heat up again to complete the cycle. In cooling mode, the system is reversed with heat taken out of the building transferred to the fluid which is injected underground to dump the extra heat to the ground. The cooled fluid then returns to the heat pump to receive more heat from the building.

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Fischer, C. E., J. M. Borrero, N. Bello González, and A. J. Kaithakkal. "Observations of solar small-scale magnetic flux-sheet emergence." Astronomy & Astrophysics 622 (February 2019): L12. http://dx.doi.org/10.1051/0004-6361/201834628.

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Aims. Two types of flux emergence were recently discovered in numerical simulations: magnetic loops and magnetic sheet emergence. While magnetic loop emergence has been documented well in recent years using high-resolution full Stokes data from ground-based telescopes as well as satellites, magnetic sheet emergence is still an understudied process. We report here on the first clear observational evidence of a magnetic sheet emergence and characterise its development. Methods. Full Stokes spectra from the Hinode spectropolarimeter were inverted with the Stokes Inversion based on Response functions (SIR) code to obtain solar atmospheric parameters such as temperature, line-of-sight velocities, and full magnetic field vector information. Results. We analyse a magnetic flux emergence event observed in the quiet-Sun internetwork. After a large-scale appearance of linear polarisation, a magnetic sheet with horizontal magnetic flux density of up to 194 Mx cm−2 hovers in the low photosphere spanning a region of 2–3 arcsec. The magnetic field azimuth obtained through Stokes inversions clearly shows an organised structure of transversal magnetic flux density emerging. The granule below the magnetic flux sheet tears the structure apart leaving the emerged flux to form several magnetic loops at the edges of the granule. Conclusions. A large amount of flux with strong horizontal magnetic fields surfaces through the interplay of buried magnetic flux and convective motions. The magnetic flux emerges within 10 minutes and we find a longitudinal magnetic flux at the foot points of the order of ∼1018 Mx. This is one to two orders of magnitude larger than what has been reported for small-scale magnetic loops. The convective flows feed the newly emerged flux into the pre-existing magnetic population on a granular scale.

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Sygulla, Felix, and Daniel Rixen. "A force-control scheme for biped robots to walk over uneven terrain including partial footholds." International Journal of Advanced Robotic Systems 17, no. 1 (January 1, 2020): 172988141989747. http://dx.doi.org/10.1177/1729881419897472.

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The robustness of biped walking in unknown and uneven terrains is still a major challenge in research. Traversing such environments is usually solved through vision-based reasoning on footholds and feedback loops—such as ground force control. Uncertain terrains are still traversed slowly to keep inaccuracies in the perceived environment model low. In this article, we present a ground force-control scheme that allows for fast traversal of uneven terrain—including unplanned partial footholds—without using vision-based data. The approach is composed of an early-contact method, direct force control with an adaptive contact model, and a strategy to adapt the center of mass height based on contact force data. The proposed method enables the humanoid robot Lola to walk over a complex uneven terrain with 6 cm variation in ground height at a walking speed of 0.5 m/s. We consider our work a general improvement on the robustness to terrain uncertainties caused by inaccurate or even lacking information on the environment.

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Han, Dongxiao, Yuwen Li, Tao Song, and Zhenyang Liu. "Multi-Objective Optimization of Loop Closure Detection Parameters for Indoor 2D Simultaneous Localization and Mapping." Sensors 20, no. 7 (March 30, 2020): 1906. http://dx.doi.org/10.3390/s20071906.

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Aiming at addressing the issues related to the tuning of loop closure detection parameters for indoor 2D graph-based simultaneous localization and mapping (SLAM), this article proposes a multi-objective optimization method for these parameters. The proposed method unifies the Karto SLAM algorithm, an efficient evaluation approach for map quality with three quantitative metrics, and a multi-objective optimization algorithm. More particularly, the evaluation metrics, i.e., the proportion of occupied grids, the number of corners and the amount of enclosed areas, can reflect the errors such as overlaps, blurring and misalignment when mapping nested loops, even in the absence of ground truth. The proposed method has been implemented and validated by testing on four datasets and two real-world environments. For all these tests, the map quality can be improved using the proposed method. Only loop closure detection parameters have been considered in this article, but the proposed evaluation metrics and optimization method have potential applications in the automatic tuning of other SLAM parameters to improve the map quality.

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Meli, R., and J. A. Ávila. "The Mexico Earthquake of September 19, 1985—Analysis of Building Response." Earthquake Spectra 5, no. 1 (February 1989): 1–17. http://dx.doi.org/10.1193/1.1585506.

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Response of simple structural models to the peculiar ground motions recorded in the lake-bed area of Mexico City was analyzed in order to explain the performance of typical buildings during the 1985 earthquake. Results for one-degree of freedom systems with different kinds of inelastic behavior show that when hysteresis loops remain stable under several cycles of large inelastic deformations, exceptionally large reductions in the structural response take place. Nevertheless, if the hysteresis loops show some degradation of strength for large displacements, the response increases sharply for the same critical periods. Results for multi-degree of freedom systems show large concentrations of ductility demands at lower stories. Static and dynamic analyses of linear and non-linear models of several typical mid-rise concrete buildings were also performed. The results agreed with reasonable accuracy with the observed behavior and with measurements of the response under low amplitude ambient vibrations.

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Snyder, Harold L. "High Temperature Isolated Switch Mode Power Supply with Integrated Power and Feedback Transformer." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, HITEC (January 1, 2014): 000214–17. http://dx.doi.org/10.4071/hitec-wp13.

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High temperature switch mode power supplies (SMPS) typically utilize magnetic solutions such as low permeability transformers for isolation from ground loops. However, imposed design constraints almost always restrict the size of switch mode power supply systems to less than the minimum space necessary for a good design, resulting in only adequate and sometimes unreliable switch mode power supply designs. Integrating the control loop and magnetic system functions is implemented by taking advantage of the bi-directional characteristics of transformers, which allows the designer an opportunity to further minimize the design space by eliminating unnecessary loop components. This is a prudent step prior to the construction of high temperature hybrids and multichip modules. Combining the operation of both the control loop and the magnetic transformer allows the designer to reduce the size of the design, regain the ability to provide a good design in the volume allotted, while still maintaining loop stability. The design procedure for this integrated control loop and magnetics system is examined, and an example circuit is simulated in SPICE with a Jiles-Atherton hysteresis model, and the circuit is realized through construction and measurements which are presented for a single forward based design targeted for operation at high temperatures.

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Olabi, M. Nadir, Osman Kirtel, and Naci Caglar. "Earthquakes Effect on the Behavior of Multi-Story RC Building Using Non-Linear Dynamic Analysis." Academic Perspective Procedia 2, no. 2 (October 27, 2019): 307–16. http://dx.doi.org/10.33793/acperpro.02.02.45.

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One of the buildings that were designed depending on the old Syrian Code is selected and modeled using SAP2000 by taking its non-linear properties to be checked under dynamical loading. Three earthquake records are taken and applied to the model as Time History loading cases. The dynamical displacement of the top roof of the building and the hysterical diagrams of the relation between base shear and roof displacement is compared and discussed. Asymmetry of shear walls and cores is responsible of the differences in responses of building elements, and insufficient nonlinear modeling of shear walls prevents from finding the real capacity of the system, although comparing pushover curves with hysteric loops from the applied ground motion excitations shows that the building is capable, depending on its old design, to withstand various types of extreme ground motions and earthquakes.

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Wu, Ray, James M. Tinjum, and William J. Likos. "Coupled Thermal Conductivity Dryout Curve and Soil–Water Characteristic Curve in Modeling of Shallow Horizontal Geothermal Ground Loops." Geotechnical and Geological Engineering 33, no. 2 (September 3, 2014): 193–205. http://dx.doi.org/10.1007/s10706-014-9811-2.

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Jabar, A., N. Tahiri, L. Bahmad, and A. Benyoussef. "Magnetic properties of a tri-decorated graphene structure: Monte Carlo study." International Journal of Modern Physics B 30, no. 32 (December 14, 2016): 1650233. http://dx.doi.org/10.1142/s0217979216502337.

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In this paper, we study the magnetic properties of a tri-decorated [Formula: see text] graphene structure using Monte Carlo simulations (MCS). Indeed, we first elaborate the ground state phase diagrams and then, we found that from [Formula: see text] phases, the only stable configurations are: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. For low reduced temperature values, the partial magnetizations are found to be in good agreement with the corresponding ground state phase diagrams. The corresponding partial susceptibilities show a notable peak around the reduced temperature value 2.0 in the absence of the external magnetic field [Formula: see text] and crystal field [Formula: see text]. To complete this study, we present and discuss the magnetic hysteresis loops.

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Escudero, Carlos, Peng Jiang, Elzbieta Pach, Ferenc Borondics, Mark W. West, Anders Tuxen, Mahati Chintapalli, Sophie Carenco, Jinghua Guo, and Miquel Salmeron. "A reaction cell with sample laser heating forin situsoft X-ray absorption spectroscopy studies under environmental conditions." Journal of Synchrotron Radiation 20, no. 3 (March 1, 2013): 504–8. http://dx.doi.org/10.1107/s0909049513002434.

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A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2Fischer–Tropsch reactions on Co nanoparticles.

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Journal articles on the topic 'Ground loops'

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