Rectangular Pad Research Articles

Dynamic characteristics of hydrostatic thrust bearing with tilting oil pad under eccentric load

Abstract During the processing of heavy machine tools, due to the effect of eccentric load, the oil film thickness changes, which directly affects the lubrication performance of the bearing. Therefore, this study takes the tiltable double rectangular oil pad hydrostatic thrust bearing as the research object and explores its dynamic characteristics. The study involves the analysis of oil film displacement response under eccentric loading conditions at different offset distances, loads and sudden loads. Through analysis, the oil film damping coefficient and oil film dynamic stiffness of each oil cavity can be determined under different offset distances and loads. The research results show that the change of oil film thickness has a significant effect on the oil film stiffness. As the oil film thickness increases, the stiffness decreases, the ability to resist deformation becomes weaker, and the displacement response time becomes longer. Moreover, the dynamic stiffness is affected by the offset distance and the loading frequency. When the offset distance is 200 mm, the load is 24 tons, and the loading frequency is 50 rad/s, the oil film stiffness of the oil cavity 1 reaches 180×108 N/m. It is worth noting that the increase in dynamic stiffness of the sinking side is significantly greater than that of the floating side. Ultimately, this study provides a theoretical reference for evaluating the stability of hydrostatic thrust bearing systems under eccentric loads.

Investigation on the influence of rotational speed on oil film stability of hydrostatic rotary table

PurposeThe purpose of this study is to investigate the influence of rotational speed on the oil film stability of the hydrostatic rotary table having double rectangular oil pads. The oil film stability is evaluated based on the oil film stiffness under constant load condition and the displacement response amplitude of the oil film under disturbance load condition.Design/methodology/approachThe oil film stability theoretical equations of the double rectangular oil cavity are deduced such as oil film stiffness, damping and dynamic equations. A simulation model is developed to analyze the relationship among oil film temperature, oil film pressure fields and oil film stability. The user-defined function programs are used to control the rotational speed, lubricant viscosity and oil film thickness during the simulation. In addition, an experimental rig is built to test the simulation results.FindingsThis study shows that oil film stability decreases with increasing rotational speed under constant load and disturbance load. The trend of oil film stability decreased slowly within 30 r/min, and then rapidly. However, since the hydrodynamic pressure effect, the decrease rate of stability is mitigated under constant load and high rotational speeds.Originality/valueThe conclusions can provide a theoretical basis for improving the oil film stability of machines with similar hydrostatic support structure.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0267/

Parametric study for shear failure of bearing pads due to hurricane-induced wave loadings

The increasing frequency of extreme weather events, such as hurricanes and rising sea levels due to climate change, presents significant challenges to coastal infrastructure. With 42% of bridges in the United States exceeding 50 years of age, which surpasses their intended service life, there is a pressing need to assess their structural integrity, especially in coastal regions. This study focuses on evaluating the structural performance of bearing pads in coastal bridges under hurricane-induced wave loadings. Utilizing a combination of physics-based models (PBM), nonlinear modal time history analysis, and numerical validation, the research examines the hysteresis response of eight distinct bearing pad configurations. The findings indicate that reinforced circular bearing pads exhibit significantly greater shear displacements compared to plain elastomeric pads, underscoring the critical influence of shape factors on shear response. Fragility functions developed in the study illustrate the probability of shear failure, with reinforced circular pads showing a 28% higher likelihood of exceedance compared to rectangular plain pads. These results highlight the necessity for advanced design methodologies specifically for bearing pads to enhance the resilience of coastal infrastructure against severe hydrodynamic forces induced by hurricanes.

Characteristics of the prototype LAMPS TPC for low-energy nuclear collisions at RAON

The time projection chambers (TPCs) with triple GEM amplifiers are tested at HIMAC using 12C beams to investigate their nucleus track reconstruction capability. The two identical TPCs, each having an active volume of 96 × 64 × 144 mm3 and rectangular pixel pads, have been developed as prototypes of the LAMPS collaboration’s low-energy active target TPC (AT-TPC). The responses to light nuclei, such as particle identification and spatial resolution, have been investigated. The Si-CsI detectors located next to the TPCs further facilitate the identification of incident particles, as well as the matching tracks. This paper presents the technical details of the experimental setup, pulse shape analysis, tracking algorithm, and spatial resolution measurement. Comparisons of the experimental data with the calculations by the Monte Carlo (MC) simulation are also discussed.

Influence of 3D surface irregularities on the performance of hydrostatic rectangular tilted thrust pad bearing configurations

Tribological behavior of tribo-pairs is strongly dependent on the surface topography. Further, the structural deformation, manufacturing, and assembly errors cause the hydrostatic thrust pad bearings to tilt slightly. The work in this article is aimed to study the effect of tilt and three-dimensional (3D) surface irregularities on the performance of hydrostatic rectangular thrust pad bearings (HRTPB) compensated with capillary restrictors. The 3D surface irregularities are assumed to follow cosine curve. To perform the analysis, a source code has been developed in MATLAB and the Finite Element Method has been used to solve the governing Reynold's equation. The numerical simulation results indicate that the effect of tilt reduces the value of fluid film reaction, fluid film stiffness, and fluid film damping coefficients. The study reveals that 3D surface irregularities results in a higher value of fluid film stiffness and damping coefficient as compared to that of smooth-bearing surfaces.

Impact of Pad Layouts and Solder Volume on Self- Alignment of Micro Solar Cells

In micro- concentrating photovoltaics (micro- PV), tiny solar cells (<1 mm2) are assembled on a circuit board on glass. To mount thousands of dies per square meter, a high throughput process is required which still yields alignment accuracy in the order of 10 μm. We developed a micro-CPV module technology where micro cells are accurately mounted directly on a circuit board on glass using a high throughput pick and place process combined with selfalignment based on the restoring force due to surface-tension of the liquid solder. In this work, we study how the selfalignment accuracy is influenced by the pad layout, solder volume and initial position of the die. We show that selfalignment significantly benefits from an induced motion, whether induced by initial displacement of the die or by flowing of molten solder along tracks. Furthermore, we found that lower solder volumes lead to higher alignment accuracies for dies on rectangular pads, whereas the dependence on solder volume is lower for pads with connected tracks where the solder flows out. Overall, alignment accuracies below 15 μm are demonstrated despite initial displacements up to 150 μm. Thus, self-alignment using surface tension of the liquid solder is suitable for micro-CPV.

Design and application of a warming fixation device for premature infants

A warming fixation device for premature infants was made and its clinical application effect was discussed. The warming fixation device for premature infants was designed and used in clinic. Sixty premature infants admitted to the neonatal ward of Baoding Hospital, Beijing Children's Hospital, Capital Medical University from January to June 2022 were selected as the control group, and 60 premature infants admitted from July to December 2022 were selected as the experimental group. In the control group, umbilical vein catheterization or central vein catheterization were performed using Astro Boy heating box, restraint band or artificial restraint. The preterm infants in the experimental group were radiated into the Astro Boy warm box with self-designed preterm warming fixation device for catheterization. The time of catheterization, the number of limb protrusion, the number of participants in catheterization operation, and the body temperature from 20 minutes of catheterization operation to the end of catheterization operation were recorded in the two groups. The frequency of hypothermia (< 36.5 centigrade) was calculated, and the differences in various indexes between the two groups were compared. (1) The warming fixation device for premature babies consists of two parts: warm sleeping bag and soft pad. The warm sleeping bag includes 4 parts: head, arm, chest and abdomen, and lower limbs. The chest and abdomen were designed with rectangular covering cloth, which can be opened to facilitate umbilical vein puncture for premature infants. There were 3 groups of restraint belts on the rectangular soft pad, which can respectively fix the arms, chest and abdomen of the warm sleeping bag and the lower limbs. During the catheterization operation, use Velcro to secure the warm sleeping bag to the cushioned surface, and select the area of exposed skin according to the piercing site. (2) There were no significant differences in gender, body weight and gestational age between the experimental group and the control group [male: 48.3% vs. 46.7%, body weight (kg): 1.86±0.06 vs. 1.82±0.06, gestational age (weeks): 31.33±0.31 vs. 32.25±0.34, all P > 0.05]. Compared with the control group, the catheterization time of experimental group was significantly shortened (minutes: 21.30±0.43 vs. 30.02±0.64, P < 0.01), the number of limb protrusion was significantly reduced (0 time: 70.0% vs. 33.3%, 1 time: 26.7% vs. 50.0%, P < 0.01), and the number of participants in catheterization operation was significantly reduced (people: 1.77±0.06 vs. 2.37±0.06, P < 0.01). The frequency of hypothermia in experimental group was significantly lower than that in the control group [6.12% (6/98) vs. 26.50% (31/117), χ2 = 15.536, P < 0.01]. The warming fixation device for premature infants is convenient to use, which can effectively shorten the tube placement time, save human resources, and reduce the incidence of hypothermia in premature infants.

Modelling, simulation and hardware analysis of misalignment and compensation topologies of wireless power transfer for electric vehicle charging application

Electric vehicles (EVs) are one of the most effective means for reducing pollution and promoting sustainable transportation in developing nations. Researchers have been paying close attention to the rapid advancement of Wireless power transfer (WPT) technology because it offers a workable solution to the challenges preventing the development of EVs. EV charging uses WPT technology that transmits electricity from the source to the load (battery) using mutual induction and does not require cables or other physical connections. Power pads, misalignment, and compensation topology are technical obstacles to EV wireless charging. In this manuscript, mathematical calculations, simulations, and experimental implementation have been done for the wireless charging of EVs. Ansys Maxwell®3D and MATLAB®/Simulink software are used to simulate various parts of the system. Finite Element Analysis (FEA) using Ansys Maxwell is used to design an existing rectangular power pad. Ansys Maxwell calculates multiple parameters such as self-inductance, mutual inductance, coupling coefficient, and magnetic flux of the transmitting and receiving coils at different misalignment positions. MATLAB®/Simulink has been used to develop a series-series compensation WPT model through which the output power and efficiency of the rectangular power pad at different misalignment positions are estimated. The experimental setup uses a DC power supply, high-frequency (HF) inverter, driver circuits, compensation circuit, MSO, power pad setup, rectifier, and resistive load to verify the simulation results.

A Comparison Study Between the Performance Characteristics of Circular and Rectangular Recess Pads of Hydrostatic Bearings

As known in mechanical engineering, any rotating shafts must be supported on bearings to reduce friction and wear and so decreasing the power losses and increasing the shaft life. These bearing may be rolling or sliding. Although the rolling bearings have low friction than sliding, but the sliding (journal) bearing can possess high working life than rolling ones if they furnished with good lubrication systems. These lubrication systems are divided into two types. The first type is the hydrodynamic lubrication which generates the oil pressure by the effect of squeeze action. Whereas the other type is the hydrostatic lubrication which generates the oil pressure by the effect of an external pressure source (pump). In the hydrostatic bearing, the oil is pressurized from the external pressure source into a pocket (or pockets) manufactured in the bearing inside the surface between the shaft and the bearing to generate a projected area for carrying the radial applied load. These pockets are generally of circular shape in most applications. In this study, a rectangular recess shape is proposed to be as the pocket instead of the circular one. The bearing characteristic performance parameters as: pressure distribution in the bearing land, the load capacity, the friction torque, the power losses, and the temperature rise are considered. A comparison between the performance of both the circular and rectangular recess pads is given based on unifying the recess shape parameter.

Performance analysis of rectangular and double-D transmitters with various receivers for electric vehicle static charging

The inductive charging stations of the future should be able to charge any car, regardless of the type of coil configuration attached to it. In this study the performance of different configurations of coils is investigated. Where the principle of interoperability is studied between the most common types of coils in the IPT system (rectangular and double-D) recommended by Society of Automotive Engineering (SAE) J2954. This interoperability analysis is done at a power level of 11.1 kVA and Z3-class ground clearance using the two types of coils on the side of the car, while double D (DD) is used as a general transmitter in one case, and in the other case, a rectangle (R) is used as a general transmitter. Four 3D finite-element models (FEMs), along with compensation circuits, are built to perform the interoperability tests. The circuit models are utilized to determine the frequency of operation and the parameters of compensation circuit that realize the rated power at highest efficiency. The concept of interoperability has been verified through multiple performance indicators, namely coupling coefficient, transmitted power, and transmission efficiency. These indicators were calculated at ideal alignment and the different cases of misalignment, whether lateral or angular. The findings prove that the two different types of receivers (R and DD) can work efficiently and smoothly with the general transmitter, whether DD pad or rectangular pad are used. At the same time, the nominal power can be transmitted at high efficiency, above the limits permitted by SAE j2954 (>85 % at alignment conditions and >80 % at misalignment conditions).

Effectiveness of the front and rear grids as a result of silicon solar cell metallization patterns: A study using Griddler simulator

The objective of this investigation is to evaluate the effect of metallization patterns on the front and rear grids on the efficiency of the silicon heterojunction (SHJ) cells. Griddler 2.5 PRO simulator was utilized to analyze the effects of various front grid metallization designs and geometries on open circuit voltage (VOC), short circuit density (JSC), fill factor (FF), and efficiency (ƞ) of silicon-based PV cells. Griddler 2.5 PRO is designed to assess different cell types, and gain a better understanding of the limiting factors that influence solar cell characteristics in laboratory and field settings. The finite-element method (FEM) is applied in solar cell modeling to approximate the cell plane as a network of resistors and diodes. It also features an interface for generating H-patterns and back metal grids. The simulations varied the number of busbars used on the front side metal grids of solar cells from 1 to 5 and the number of metal fingers used for grid pattern optimization from 80 to 130, with finger widths ranging from 10 to 60 µm. For optimization of efficiency and fill factor, various styles (straight, rectangular pad tapered, round pad, digital, two split, and three split) and shapes (straight, pointed, digital, apollo, and wine bottle) were explored. The front and rear contact resistances were kept constant during these simulations to obtain the best fill factor and efficiency. In this model, with 110 fingers (the finger sheet resistance of front and rear sides is kept at 3 mΩ/□) and four busbars, with two split style and straight shapes and a finger width of 25 µm, was designed to achieve maximum performance of the solar cell. Various recombination loss factors in the cells are also analyzed. The results indicate that this is one of the most efficient silicon solar cells modeled, with a fill factor and efficiency of 80 % and 19.55 %, respectively, which is noteworthy for a planar solar cell.

Optimized recess etching criteria for T‐gate fabrication achieving ft = 290 GHz at Lg = 124 nm in metamorphic high electron mobility transistor with In0.7Ga0.3As channel

AbstractThe authors propose criteria for recess etching to fabricate T‐gate used in InGaAs high electron mobility transistors (HEMTs). By patterning additional rectangular pads on the source and drain metals in the e‐beam lithography step, it is possible to measure the drain‐to‐source resistance (Rds) and current (Ids). The ratio (Γ) of before and after etching for each Rds and Ids can be used as criteria to determine the point in time to stop etching. By performing recess etching with Γ= 1.97 for Rds and Γ= 0.38 for Ids on an epiwafer having cap doping concentration of 2 × 1019 cm−3 and channel indium content of 0.7, the authors have fabricated InGaAs metamorphic high electron mobility transistor (mHEMT) device showing gm,max= 1603 mS/mm and ft= 290 GHz at Lg= 124 nm. The criteria presented can be applied to InGaAs HEMTs with various epitaxial structures.

Proximity-induced superconductivity in (Bi1\u2212xSbx)2Te3 topological-insulator nanowires

When a topological insulator is made into a nanowire, the interplay between topology and size quantization gives rise to peculiar one-dimensional states whose energy dispersion can be manipulated by external fields. In the presence of proximity-induced superconductivity, these 1D states offer a tunable platform for Majorana zero modes. While the existence of such peculiar 1D states has been experimentally confirmed, the realization of robust proximity-induced superconductivity in topological-insulator nanowires remains a challenge. Here, we report the realization of superconducting topological-insulator nanowires based on (Bi1−xSbx)2Te3 (BST) thin films. When two rectangular pads of palladium are deposited on a BST thin film with a separation of 100–200 nm, the BST beneath the pads is converted into a superconductor, leaving a nanowire of BST in-between. We found that the interface is epitaxial and has a high electronic transparency, leading to a robust superconductivity induced in the BST nanowire. Due to its suitable geometry for gate-tuning, this platform is promising for future studies of Majorana zero modes.

Cost-Efficiency Optimization of Ground Assemblies for Dynamic Wireless Charging of Electric Vehicles

Dynamic wireless power transfer (DWPT) allows electric vehicles (EVs) to be charged while in motion. However, high cost and efficiency concerns limit the widespread adoption of DWPT. A ground assembly (GA) accounts for most of the system cost since it is implemented on a significant portion of the road. This article proposes a cost-efficiency optimization algorithm to determine the optimum design of a DWPT transmitter (Tx) pad. Elongated rectangular pads are considered a compromise between cost and efficiency. An optimization methodology is put forward to maximize Tx pad efficiency while minimizing GA cost over a selected road. The optimum design allows constant power transfer inside a selected rated power zone while considering EV lateral misalignment as a random variable. Main cost factors are accounted for, including the cost of the pad coil Litz wire and ferrite material and Tx power electronics and compensation network. Particle swarm optimization allowed the number of finite element analysis simulations to be reduced by intelligently selecting test designs. Statistical analysis is applied to understand the impact of different variables on the final design and the interdependence between variables. Additional analyses are conducted to evaluate the impact of different DWPT aspects, including the wire gauge, probability density of the misalignment variable, multilayer coil design, and capacitor cost modeling. The algorithm is used to design a 3.7-kVA Tx pad with respect to the SAE J2954 receiver test stand VA WPT1/Z1. The optimization Pareto fronts illustrate the family of optimum designs, while the chosen 3.7-kVA pad offers the statistical expected value of pad efficiency as 96%, GA per meter cost of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 1004, and an optimum pad length of 1.75 m. The 3.7-kVA optimized pad is manufactured and tested for several operating conditions verifying the simulation results.

A Comparative Study of Straight-Strip and Zigzag-Interleaved Anode Patterns for MPGD Readouts

Due to their simplicity and versatility of design, straight strip or rectangular pad anode structures are frequently employed with micro-pattern gas detectors to reconstruct high precision space points for various tracking applications. The particle impact point is typically determined by interpolating the charge collected by several neighboring pads. However, to effectively extract the inherent positional information, the lateral spacing of the straight pads must be significantly smaller than the extent of the charge cloud. In contrast, highly interleaved anode patterns, such as zigzags, can adequately sample the charge with a pitch comparable to the size of the charge cloud or even larger. This has the considerable advantage of providing the same performance while requiring far fewer instrumented channels. Additionally, the geometric parameters defining such zigzag structures may be tuned to provide a uniform detector response without the need for so-called pad response functions, while simultaneously maintaining excellent position resolution. We have measured the position resolution of a variety of zigzag shaped anode patterns optimized for various MPGDs, including GEM, Micromegas, and micro-RWELL and compared this performance to the same detectors equipped with straight pads of varying pitch. We report on the performance results of each readout structure, evaluated under identical conditions in a test beam.

Influence of new surface micro-structures on the performance behaviours of fluid film tilting pad thrust bearings

Performance parameters such as power loss, minimum film thickness, and maximum oil temperature of the sector-shaped tilting pad thrust bearings employing the new micro-structural geometries on pad surfaces have been investigated. The lubrication equation incorporating the mass-conservation issue is discretized using the finite element method and the solution of resulting algebraic equations is obtained employing a Newton-Schur method. The pad equilibrium in the analysis is established using the Newton-Raphson and Braydon methods. The influence of attributes of micro-structures such as depth, circumferential and radial positioning extents have been explored on the performance behaviours. It is found that with the new micro-structured pad surfaces, the performance parameters significantly improved in comparison to conventional plain and conventional rectangular pocketed pads.

Interoperability Improvement for Rectangular Pad and DD Pad of Wireless Electric Vehicle Charging System Based on Adaptive Position Adjustment

Wireless charging for electric vehicles has been investigated in recent years. One of the critical issues of the research is to improve the weak interoperability between two popular charging pads—rectangular pad (RCP) and double-D pad (DDP). This article intends to model the interoperability under pad misalignment and improve it by adjusting the pads’ relative position. First, the variation of interoperability with pad misalignment is analyzed by the flux model. Full output power and high transmission efficiency can be achieved when the two pads are misaligned to a certain distance. Second, the optimal misalignment is obtained by flux calculation and simulation. Third, an adaptive position adjustment method for the transmitting pad based on the variable-step perturbation and observation algorithm is proposed. By searching the maximum dc input current, the optimal position of the transmitting pad can be found. Finally, in the experiment, a 3.3 kW output with 95% coil-coil efficiency is realized when the RCP and DDP interoperate at the optimal position. Compared with the scenario without position adjustment, the improvement of output power and efficiency proves that the proposal can optimize the interoperability between the RCP and DDP.

Optimal Design of IPT Bipolar Power Pad for Roadway-Powered EV Charging Systems

This article proposes a multiobjective design optimization of rectangular bipolar power pads (BPP) for dynamic inductive power transfer (IPT) with application in electric vehicles. Minimization of IPT's design cost, loss that includes core and winding, and maximization of the IPT system's tolerance against horizontal/vertical misalignment are considered as objective functions during the optimization process. The design variables of the proposed algorithm are the shield plate length and width, ferrite bar length and width, the overlapping length of the coils, and the coil width and inner length of the coil. Power electronic limitations by defining the IPT's quality factor ( 4 <; Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> <; 10), maximum allowable electromagnetic field (EMF) exposure ( EMF ≤ EMF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Max</sub> ), efficiency of all possible solutions greater than 80% ( η > 80%), and upper/lower limits of design parameters are considered as the constraints of this optimization problem. The time-harmonic electromagnetic physics model of the BPP is analyzed using an finite element method magnetics (FEMM) software coupled with MATLAB. A nondominated genetic algorithm (NSGA-II) is employed as the optimization solver, in which the electromagnetic measurements from the FEMM software are used to evaluate the fitness values of the proposed objectives. The proposed BPP design optimization is applied on a 10-kW IPT system as a case study. The optimization results produced 15 Pareto optimal solutions. A validation study of two Pareto front solutions (PFS) is also presented. The Pareto optimal solutions allow the designer to select the best design parameters based on the objectives of highest priority.

Design Studies of High-Resolution Readout Planes Using Zigzags With GEM Detectors

We have developed highly interleaved zigzag-shaped electrodes for collecting charge on the readout plane of various micropattern gaseous detectors (MPGDs), including gas electron multiplier (GEM) and micromega detectors. An optimized zigzag pad (or strip) anode can greatly enhance charge sharing among neighboring pads compared to traditional straight strip or rectangular pad designs and as a result can deliver excellent position resolution with minimal channel count, while exhibiting a virtually uniform response across the detector. We have systematically studied the effects of varying the parameters that define the zigzag geometry using simulations and have measured several printed circuit boards (PCBs) comprising a range of zigzag designs. Recently, we have employed laser ablation to generate zigzag patterns with pad-to-pad gaps smaller than 1 mil (or 25 μm). Reducing the gap well below the 3-mil limit imposed by traditional chemical etching has allowed the production of zigzag electrodes with unprecedentedly small feature sizes. In turn, laser-etched zigzag PCBs were shown to exhibit markedly improved performance over earlier generation PCBs, with position resolutions below 50 μm for a 2-mm pitch. This article will explore in detail the dependence of the position resolution on the structural parameters of a zigzag-shaped anode, specifically for the case of a quadruple GEM detector.

Effects of Electrode Configurations and Injected Current Intensity on the Electrical Field of Transcranial Direct Current Stimulation: A Simulation Study.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technology that modulates the excitability of the brain by delivering weak electric currents to the brain via scalp electrodes. Electrode configuration and injected current intensity are two important parameters in the tDCS design. This simulation study examined three commercially available electrode configurations, i.e. conventional low definition rectangular pad, high-definition Disc, and high-definition 4 x 1 with different electrode distances and different injected current intensity. Simulation results show that increasing the injected current intensity of HD-tDCS mainly increases the electrical field strength for all configurations. Both Disc and 4 x 1 high definition tDCS (HD-tDCS) have better focality than the conventional low-definition rectangular pad. Increasing the inter-electrode distance in HD-tDCS enlarges the electrical field strength and the depth of stimulation but reduces the focality. In motor rehabilitation, a trade-off needs to be made in the tDCS design to allow the electrical field reaching the white matter to facilitate the usage of the cortico-spinal tract without influencing other undesirable regions in the brain.