Parallel Coils Research Articles

Thermal performance of a conic basket heat exchanger coupled to a geothermal heat pump for greenhouse cooling under Tunisian climate

This paper presents an experimental analysis to examine the performance of a new conic basket geothermal heat exchanger (CBGHE) for greenhouse cooling. This system has never been used or exploited in Tunisia for any research or industrial purposes. Therefore, an experimental system was designed, installed and tested in the Research and Technology Center of Energy (CRTEn) of Borj Cedria.The configuration typically consists of a series of parallel coil implanted in 3 meter depth. The experiments are conducted between 7th and 8th June 2014. The results obtained show that the CBGHE system can be used in the Mediterranean regions such as Tunisia for greenhouses cooling. During the experimental period the maximum quantity of heat transferred to the ground by the CBGHE is about 8kW. The maximum average temperature difference between the inlet and outlet CBGHE system is approximately 30°C, with measured mass flow rate of 0.08kg/s. The air temperature inside the greenhouse decreased of about 12°C.After the stabilization of the CBGHE system, the performances coefficients of the geothermal heat pump (COPhp) and the overall system (COPsys) are 3.9 and 2.82, respectively.

Dynamic model and experimental validation of an indirect thermosyphon solar water heater coupled with a parallel circular tube rings type heat exchange coil

This article introduces the design of an indirect thermosyphon solar water heating system coupled with a parallel circular tube rings type heat exchanger. The proposed heat exchange coil set is able to provide similarly of heat exchange areas of a comparable size helical coil but reduces the friction loss of the thermosyphon fluid flow. The design can also maintain the thermal stratification along the vertical height of the storage water tank. Hence, the thermal efficiency of the solar water heater is improved as compared with a same system but coupled with a comparable size helical coil and shell type storage water tank. Detailed mathematical model development from individual components to the integration of whole system are described. The transient system model is simulated by a self-developed FORTRAN program. The experimental and simulations results of the solar thermal system are fully presented in this paper. Comparison of both results shows good agreements and convinces the accuracy of the entire system models as well as the suitability of the computational method. The effectiveness of the proposed heat exchange coil set is evaluated by its NTU value which is computed by program simulation. The NTU value reveals that the overall efficiency of the solar thermal system can be improved by further physical design optimization. Simulation results analyses also consolidate the enhancement of the thermosyphon flow rate (in other words, the efficiency) of the proposed design over the helical coil design as expected.

A 32-channel combined RF and B0 shim array for 3T brain imaging.

We add user-controllable direct currents (DC) to the individual elements of a 32-channel radio-frequency (RF) receive array to provide B0 shimming ability while preserving the array's reception sensitivity and parallel imaging performance. Shim performance using constrained DC current (± 2.5A) is simulated for brain arrays ranging from 8 to 128 elements. A 32-channel 3-tesla brain array is realized using inductive chokes to bridge the tuning capacitors on each RF loop. The RF and B0 shimming performance is assessed in bench and imaging measurements. The addition of DC currents to the 32-channel RF array is achieved with minimal disruption of the RF performance and/or negative side effects such as conductor heating or mechanical torques. The shimming results agree well with simulations and show performance superior to third-order spherical harmonic (SH) shimming. Imaging tests show the ability to reduce the standard frontal lobe susceptibility-induced fields and improve echo planar imaging geometric distortion. The simulation of 64- and 128-channel brain arrays suggest that even further shimming improvement is possible (equivalent to up to 6th-order SH shim coils). Including user-controlled shim currents on the loops of a conventional highly parallel brain array coil is feasible with modest current levels and produces improved B0 shimming performance over standard second-order SH shimming.

Increase in High-Frequency Magnetic Fields due to Parallel Coils Added to Applicator for Hyperthermia Therapy

Increase in High-Frequency Magnetic Fields due to Parallel Coils Added to Applicator for Hyperthermia Therapy

Double tungsten coil atomic absorption spectrometer based on an acousto-optic tunable filter

An atomic absorption spectrometer based on a quartz acousto-optic tunable filter (AOTF) monochromator operating in the 271–453nm range, is described. The instrument was tailored to study the formation and evolution of electrothermal atomic cloud induced either by one or two tungsten coils. The spectrometer also includes a fast response programmable photomultiplier module for data acquisition, and a power supply capable of driving two parallel tungsten coils independently. The atomization cell herein described was manufactured in PTFE and presents a new design with reduced size. Synchronization between the instant of power delivering to start the atomization process and the detection was achieved, allowing for monitoring the atomization and thermal events synchronously and in real time. Absorption signals can be sampled at a rate of a few milliseconds, compatible with the fast phenomena that occur with electrothermal metallic atomizers. The instrument performance was preliminarily evaluated by monitoring the absorption of radiation of atomic clouds produced by standard solutions containing chromium or lead. Its quantitative performance was evaluated by using Cr aqueous solutions, resulting in detection limits as low as 0.24μgL−1, and a relative standard deviation of 3%.

Dynamic performance of high speed solenoid valve with parallel coils

The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.

Single and two-phase flow fluid dynamics in parallel helical coils

The design of helical coiled steam generators requires the knowledge of the single and two-phase fluid dynamics. The present work reports the results of an experimental campaign on single-phase and two phase pressure drops and void fraction in three parallel helicoidal pipes, in which the total water flow rate is splitted by means of a branch. With this test configuration the distribution of the water flow rate in the helicoidal pipes and the phenomena of the instability of the two-phase flow have been experimentally investigated.

운송용 트럭에 대한 엔진오일의 전기·자기적 특성연구

Abstract : In this paper, we investigate the electric and magnetic properties of the engine oil, and estimate its changing time in transport truck. The four diesel trucks are selected, and the capacitance and inductance are investigated with parallel capacitor and induction coil, respectively. The measured capacitance gradually increases up to 10,000~14,000 km due to the activation of antioxidant, and then decreasing phenomena happen. The inductance decreases and the saturation began in 10,000~14,000 km range. Although the behavior of inductance is different from that of capacitance, but changing points are similar. From those results, we can estimate the changing time of engine oil is around 10,000~14,000 km and the inductance can be used for monitoring of engine oil in transport trucks.Key words: Engine oil(sAw±tui ), Oil deterioration(tuisa„A ), Capacitance(vun t–e¶ ), Inductance(ueaB!p‘ ), Environmental pollution( „EZatse ) Nomenclature 1) C : capacitance, pFL : inductance, FH§ : dielectric constant µ : magnetic permeability

Identification of Ligand Specificity Determinants in Lantibiotic Bovicin HJ50 and the Receptor BovK, a Multitransmembrane Histidine Kinase

Lantibiotic bovicin HJ50 is produced by Streptococcus bovis HJ50 and acts as the extracellular signal to autoregulate its own biosynthesis through BovK/R two-component system. Bovicin HJ50 shows a linear N-terminal and glubolar C-terminal structure, and the sensor histidine kinase BovK contains eight transmembrane segments lacking any extensive surface-exposed sensory domain. The signal recognition mechanism between bovicin HJ50 and BovK is still unknown. We performed saturated alanine scanning mutagenesis and other amino acid substitutions on bovicin HJ50 using a semi-in vitro biosynthesis. Results of the mutants inducing activities indicated that several charged and hydrophobic amino acids in ring B of bovicin HJ50, as well as two glycines were key residues to recognize BovK. Circular dichroism analyses indicated that both glycines contributed to bovicin HJ50 structural changes in the membrane. Biotin-labeled bovicin HJ50 could interact with the N-terminal sensor of BovK, and several charged residues and a conserved hydrophobic region in the N-terminal portion of BovK sensor domain were important for interacting with the signal bovicin HJ50. By combining the results, we suggested a mechanism of bovicin HJ50 recognizing and activating BovK mainly through electrostatic and hydrophobic interactions.

A Study on the Effective Long Type Coil Shape by Multidisciplinary Method in Induction Heating

The axis symmetric analysis method can neither handle initial curved plates nor be used in the optimization of coil shapes because an axis symmetric coil is the only shape to analyze in this method. But the method using some discrete divisions and steps, can overcome these difficulties and show more accurate, reasonable results of temperatures and deflections in flat or curved plates with initial curvature, than those in the axis symmetric analysis method. Traditionally, the coil shape in induction heating is circular shape and it needs the moving process along heating lines. To overcome these, the “long type coil” with some linear parallel coils is proposed. It does not need the moving process along heating lines and reduces the heating process time. The results of experiments are compared with those of simulation.

THE EQUIVALENT SELF-INDUCTANCE OF <I>N</I> COUPLED PARALLEL COILS

Based on Faraday’s law of electromagnetic induction and the existence condition of nontrivial solution to a homogeneous and linear differential system of equations, the equivalent selfinductance of N coupled parallel coils has been derived by using some algebraic techniques. It can be expressed as the ratio of the determinants of two matrices, with ranks of N and N − 1, respectively, and constructed with the self and mutual inductance of those coils. In addition, special conclusions are deduced and/or discussed in detail for three particular cases: 1. the completely uncoupled case, 2. the identical and symmetrical case, and 3. the completely coupled case, which are coincident with the existing results in the references.

Neural Network Modeling of Deposition Rate Characteristics of Low Temperature Silicon Nitride Deposited by Inner Two Parallel Coil Inductively Coupled Plasma Chemical Vapor Deposition

In this study, a neural network model for silicon nitride (SiN) deposition process is proposed. SiN thin films were deposited by a direct inner two parallel inductively coupled plasma chemical vapor deposition (ICPCVD) system that can control the activated radical and charged species in plasma. This system can produce SiN thin films at low temperature for flexible displays. The input parameters considered for deposition conditions were the N2 gas flow rate, NH3 gas flow rate, and substrate temperature. These were varied within the ranges of 0-20 sccm, 0-20 sccm, and 100-300 degrees C, respectively. For those of input parameters and the output of deposition rate, we developed a back propagation neural network model with a pre-processor. It is shown that the model accuracy and learning speed of the proposed model are better than those of a conventional neural network model. In the experiments conducted, it was found that the deposition rate increased as the flow rates of ammonia (NH3) and nitrogen (N2) increased up to a certain amount. On the contrary, when the flow rates of NH3 and N2 went over a certain amount, the deposition rate decreased. It was also found that an increase in temperature resulted in an increase in the deposition rate.

A comparative numerical study of rotating and stationary RF coils in terms of flip angle and specific absorption rate for 7 T MRI

While high-field magnetic resonance imaging promises improved image quality and faster scan time, it is affected by non-uniform flip angle distributions and unsafe specific absorption rate levels within the patient, as a result of the complicated radiofrequency (RF) field – tissue interactions. This numerical study explored the possibility of using a single mechanically rotating RF coil for RF shimming and specific absorption rate management applications at 7T. In particular, this new approach (with three different RF coil element arrangements) was compared against both an 8-channel parallel coil array and a birdcage volume coil, with and without RF current optimisation. The evaluation was conducted using an in-house developed and validated finite-difference time-domain method in conjunction with a tissue-equivalent human head model. It was found that, without current optimisation, the rotating RF coil method produced a more uniform flip angle distribution and a lower maximum global and local specific absorption rate compared to the 8-channel parallel coil array and birdcage resonator. In addition, due to the large number of degrees of freedom in the form of rotated sensitivity profiles, the rotating RF coil approach exhibited good RF shimming and specific absorption rate management performance. This suggests that the proposed method can be useful in the development of techniques that address contemporary RF issues associated with high-field magnetic resonance imaging.

Electrical and Mechanical Characteristics of Room Temperature Deposited Silicon Nitride Using Two Inner Parallel Cylindrical Coils Inductively Coupled Plasma Chemical Vapor Deposition

For investigating silicon nitride (SiN) thin film deposition process at room temperature without additional substrate heating, we studied inductively coupled plasma chemical vapor deposition with two inner parallel cylindrical coils which can activate the more radicals and charged species in the plasma. We investigated the influence of plasma RF power on the characteristics of room temperature deposited SiN films. Deposition rates, dielectric constant, refractive index, and stress of the films ranged from 4.5 nm/min to 8.3 nm/min, 8.4 to 10, 1.8 to 2.1, and 0.54 to 0.15, respectively. According to the FTIR measurements, the concentration of the Si--H and N--H bonds was decreased as the RF power increased, and the Si--H bonds tended to disappear at RF power over 500 W. This reduction in the hydrogen content was accompanied by the increases in the deposition rate and refractive index. It was confirmed that the breakdown field could be also maximized to 10 MV/cm.

Analysis of eddy current interaction between a parallel coil and a ferromagnetic pipe with remanence

Eddy current field excited by a parallel coil placed next to a ferromagnetic pipe with remanence is studied in this paper. The influence of the remanence is analyzed at first. The analytical solutions to the ferromagnetic pipe eddy current field are deduced by means of a second-order vector potential formalism, and the analytical expression for the impedance change of the excitation coil is constructed. Theoretical analysis of the influence for the remanence and the analytical solutions to the eddy current field are verified by experiments.

Analysis of fouling factor in district heating heat exchangers with parallel helical tube coils

This paper presents the results of measurements of thermal performance of 8 heat exchangers with parallel helical coils. Measurements were conducted in substations in 2 district heating systems in Serbia: Belgrade and Sremska Mitrovica. The values of fouling resistances were found to be slightly lesser than usual values for typical shell-and-tube heat exchangers with straight tubes. Analysis of thermal performance of heat exchangers showed that the shell-side heat transfer coefficient can be calculated using the correlation based on hydraulic diameter.

Strong contributions from vertical triads to helix-partner preferences in parallel coiled coils.

Pairing preferences in heterodimeric coiled coils are determined by complementarities among side chains that pack against one another at the helix-helix interface. However, relationships between dimer stability and interfacial residue identity are not fully understood. In the context of the "knobs-into-holes" (KIH) packing pattern, one can identify two classes of interactions between side chains from different helices: "lateral", in which a line connecting the adjacent side chains is perpendicular to the helix axes, and "vertical", in which the connecting line is parallel to the helix axes. We have previously analyzed vertical interactions in antiparallel coiled coils and found that one type of triad constellation (a'-a-a') exerts a strong effect on pairing preferences, while the other type of triad (d'-d-d') has relatively little impact on pairing tendencies. Here, we ask whether vertical interactions (d'-a-d') influence pairing in parallel coiled-coil dimers. Our results indicate that vertical interactions can exert a substantial impact on pairing specificity, and that the influence of the d'-a-d' triad depends on the lateral a' contact within the local KIH motif. Structure-informed bioinformatic analyses of protein sequences reveal trends consistent with the thermodynamic data derived from our experimental model system in suggesting that heterotriads involving Leu and Ile are preferred over homotriads involving Leu and Ile.

Parallel and partial Fourier imaging with prospective motion correction

Subject motion during scan is a major source of artifacts in MR examinations. Prospective motion correction is a promising technique that tracks subject motion and adjusts the imaging volume in real time; however, additional retrospective correction may be necessary to achieve robust image quality and compatibility with other imaging options. Real-time realignment of the imaging volume by prospective motion correction changes the coil sensitivity weighting and the field inhomogeneity relative to the imaging volume. This can pose image reconstruction problems with parallel imaging and partial Fourier imaging, which rely on coil sensitivity and image phase information, respectively. This work presents a practical method for reconstructing images acquired using prospective motion correction with parallel imaging and/or partial Fourier imaging. Our proposed approach is data driven and noniterative; data are binned into several position bins based on motion measurements made during the prospective motion correction acquisition and the data in each bin are processed through intrabin operations such as parallel imaging reconstruction (in case of undersampling), phase correction, and coil combination before combination of the position bins. We demonstrate the effectiveness of our technique through simulation studies and in vivo experiments using a prospectively motion-corrected three-dimensional fast spin echo sequence.

Experimental and Theoretical Evaluation of Multisite Cadmium(II) Exchange in Designed Three-Stranded Coiled-Coil Peptides

An important factor that defines the toxicity of elements such as cadmium(II), mercury(II), and lead(II) with biological macromolecules is metal ion exchange dynamics. Intriguingly, little is known about the fundamental rates and mechanisms of metal ion exchange into proteins, especially helical bundles. Herein, we investigate the exchange kinetics of Cd(II) using de novo designed three-stranded coiled-coil peptides that contain metal complexing cysteine thiolates as a model for the incorporation of this ion into trimeric, parallel coiled coils. Peptides were designed containing both a single Cd(II) binding site, GrandL12AL16C [Grand = AcG-(LKALEEK)(5)-GNH(2)], GrandL26AL30C, and GrandL26AE28QL30C, as well as GrandL12AL16CL26AL30C with two Cd(II) binding sites. The binding of Cd(II) to any of these sites is of high affinity (K(A) > 3 × 10(7) M(-1)). Using (113)Cd NMR spectroscopy, Cd(II) binding to these designed peptides was monitored. While the Cd(II) binding is in extreme slow exchange regime without showing any chemical shift changes, incremental line broadening for the bound (113)Cd(II) signal is observed when excess (113)Cd(II) is titrated into the peptides. Most dramatically, for one site, L26AL30C, all (113)Cd(II) NMR signals disappear once a 1.7:1 ratio of Cd(II)/(peptide)(3) is reached. The observed processes are not compatible with a simple "free-bound" two-site exchange kinetics at any time regime. The experimental results can, however, be simulated in detail with a multisite binding model, which features additional Cd(II) binding site(s) which, once occupied, perturb the primary binding site. This model is expanded into differential equations for five-site NMR chemical exchange. The numerical integration of these equations exhibits progressive loss of the primary site NMR signal without a chemical shift change and with limited line broadening, in good agreement with the observed experimental data. The mathematical model is interpreted in molecular terms as representing binding of excess Cd(II) to surface Glu residues located at the helical interfaces. In the absence of Cd(II), the Glu residues stabilize the three-helical structure though salt bridge interactions with surface Lys residues. We hypothesize that Cd(II) interferes with these surface ion pairs, destabilizing the helical structure, and perturbing the primary Cd(II) binding site. This hypothesis is supported by the observation that the Cd(II)-excess line broadening is attenuated in GrandL26AE28QL30C, where a surface Glu(28), close to the metal binding site, was changed to Gln. The external binding site may function as an entry pathway for Cd(II) to find its internal binding site following a molecular rearrangement which may serve as a basis for our understanding of metal complexation, transport, and exchange in complex native systems containing α-helical bundles.

Induction heating with the ring effect for injection molding plates

Induction heating in injection molding has the advantages of rapid heating, reduced cycle time, and improved product quality. In this research, using both experiment and simulation, externally wrapped coil induction heating was applied to verify the heating capacity of a pair of mold plates. By applying different coil designs and mold gap, the effect of the externally wrapped coil induction heating was evaluated. Results showed that when a serial coil was used as an inductor, the heating rate reached 8.0°C/s. From an initial mold temperature of 40°C, after 15s heating, the mold surface temperature reached 159.9°C with the serial coil. The parallel coil shows a better heating uniformity but its heating rate is far lower than the serial coil. For the serial coil, the temperature distribution between the core and cavity plate are almost the same. The heating rate increases from 4.9°C/s to 10.6°C/s when the inductor design is changed from 5 turns to 7 turns. After 15s heating, the temperature at point T2 increases from 40°C to 166.7°C and 106.1°C with a mold gap of 1mm, and 6mm, respectively.