The electrochemical capacitive performance measure- ments were carried out by a CHI 660D instrument using a three-electrode system. The three-electrode system in- cludes platinum film as the counter electrode, saturated calomel electrode (SCE) as the reference electrode, and the as-prepared sample as the working electrode. The car- bon materials were mixed with polytetrafluoroethylene as a binder at a weight ratio of 95:5. After drying at 80 °C overnight, the mixture was smeared on a nickel foam and pressed at 100 kg/cm 2 to form a slice as a working elec- trode. The loading amount of active materials for a single electrode was 2 mg. The electrochemical performances of the carbon materials were measured in a 30 wt% KOH so- lution. A potential window of −1~0 V vs. SCE was selected for the electrochemical measurements. The average spe- cific capacitance (C) was derived from the discharge curve according to the following equation:
becoming technologically important for low-power gadgets like PC cards, photographic flash, flashlights, portable media players and automated meter reading equipments, although their widespread usage has not been attained due to a high cost to performance ratio (Hall et al., 2010). Exploding research is thus being conducted to lower the costs of the capacitors through the engineering of new materials. Needless to say that selection of appropriate electrode materials and electrolyte systems is fundamental in determining the device performance. Currently the most viable materials used as electrodes in electrochemical capacitors are metal oxides (Novak 1997) and conductive polymers (Zhou et al., 2004), in addition to the other conventional carbon materials like activated carbons (ACs) (Wang et al., 2007), carbon aerogels (Fang et al., 2007), graphites (Mitra and Sampath 2004), carbon nanotubes (Honda et al., 2007) carbon nanofibers (Kim and Lee 2004), and nano sized carbons (Sivakkumar
nanostructures with uniform using hydrothermal-growth method. The as-prepared material can improve not only the initial discharge capacity, but also the cycling stability during subsequent cycles. Furthermore, this research effort can give rise to an enhanced performance in the case of graphene/Mn 3 O 4 composite. A high specific capacitance of 355.5 F g -1 at 0.35 A.g -1 measured for the
The CV curves of RMGO150- RMGO450 were recorded at various scan rates of 5, 10, 20, 50 and 100mV/s. As shown in Fig. 5b-5e, the current density increases with increasing scan rate, which suggests the presence of ideal capacitive behaviour. The specific capacitance of RMGO can be calculated using the following equation: I V dV
appropriate for improvement of electrochemical super- capacitors (Table 1). Electrochemical Impedance Spec- troscopy (EIS) was performed to determine the parameters for electron transfer reactions at the inter- face of the working electrode. EIS spectra of PPy and HPyC3% are measured in the frequency ranges from 0.1 to1000 Hz with pulse amplitude of 0.03 mV. Nyquist diagram for the PPy and HPyC3% electrodes are shown in Fig. 7. The Nyquist diagram of both the electrodes consist of the two parts, one is quasi semi- circle in the high frequency region and another shows linear part at low frequency region. The electrolyte re- sistance (Rs), can be found from the semicircle inter- ception point on the real axis while the charge transfer resistance (Rct), was calculated by measuring the mag- nitude of the diameter of semicircle on the electrode surface. PPy illustrate high impedance values compared with those obtained for the HPyC3%. The curves achieved for the HPyC3% also showed a deviation in slope from a vertical position in relation to PPy, which is attributed to the low Rct values and may be ascribed to the high porosity and mobility inside the electrodes. This supports electronic transfer in the HPyCs, thus significantly reducing the Rct value, making it more capacitive. The increase in electron transfer in HPyC3% is perhaps attributable to the charge transfer between Hb and PPy. This can be partly proven by the FT-IR spectrum, which suggests interaction of electrons
In this work capacity of tokamak plasma is calculated using modeling of tokamak configuration as toroidal and coaxial capacitor. This value is very important and plays an important role in time- varying regimes in tokamak. For exact simulation of plasma behavior, this amount will be added to circuit equations and transport codes. Since capacitive properties of tokamak cause production of a radial electric field, it deserves our special attention.
directly as electrocatalysts for ORR, the as-prepared carbon exhibited poor performance due to encapsulation of the catalytic active centers by the amorphous carbon and the existence of less active iron compounds. The catalytic performance of the porous carbon was then enhanced significantly by etching with air plasma which removes the less active carbon domains and change the chemical state of the residual iron compounds. In this study, we demonstrate that high catalytic performance can be also achieved by treating chitin at a higher temperature (1000 °C) instead of etching by plasma. Furthermore, the as-prepared carbon also exhibited excellent capacitive performance as electrodes for supercapacitors.
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and scan rate for both forward and reverse sweeps is shown in Fig. 3(d). The well-known Randles–Sevcik equation shows that for solution based faradaic processes, the peak redox current will display a linear relationship with the square root of the scan rate. 37,38 The redox events observed here showed a linear relationship between peak redox current and scan rate. These are attributed to surface faradaic processes, as described in literature, 39 and are attributed to reversible redox reactions at the functional groups on the N-rGO material. It has previously been reported that retaining some amount of oxygen moieties enhances the capacitive performance of graphene material in addition to the presence of nitrogen groups. 40 The partially reduced nature of our N-rGO ensures the presence of some residual oxygen functional groups which provide another pseudo-capacitive contribution to the total material capacitance. The capacitance per unit area reported here is approximately twice that reported previously using the same technique for non- functionalised liquid phase exfoliated graphene electrodes. 33 The performance of the N-rGO electrode was further evaluated by comparing it to that of untreated GO. Electrodes fabricated from GO in the same manner as before displayed an appreciably Fig. 3 (a) Voltammograms for repeated cycling of N-rGO working electrode in 1 M H 2 SO 4 electrolyte at a scan rate of 100 mV s 1 . Cycle number corres-
New methods to measure the IPC values were proposed and tested based on the cosmic ray events and hot pixels, where the dark frame data sampled up-the-ramp were used. With these two methods, the variations of capacitive coupling strength were studied for different temperatures. It can be seen that the IPC magnitude decreases with increasing detector temperature, as can be predicted from the IPC model. The IPC dependencies on the center pixel intensity and background were also checked. It appears that the coupling becomes weaker when the target pixel event gets stronger, while the trend reverses with the change of background level. The former is predictable from the theory that the gaps between pixels increase during the charge collection. However, the variation of IPC with different backgrounds contradicts this theory. Further experiment and analysis need to verify and explain this variation.
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was CelgardR 2325. 2016 coin-type cells were assembled in an Ar-filled glove box using lithium metal foil as the counter electrode. The measurements of electrochemical performance were carried out on a program-controlled Battery Test System (Land®, Wuhan, China) at room temperature. The cyclic voltammetry (CV) was conducted in a three-electrode cell with lithium foil as counter and reference electrodes by using a CHI660B Electrochemical Work-station (Chenghua, Shanghai, China) at room temperature.
A concentric coplanar capacitive sensor includes a charged central disc forming a first electrode, an outer annular ring coplanar with and outer to the charged central disc, the outer annular ring forming a second electrode, and a gap between the charged central disc and the outer annular ring. The first electrode and the second electrode may be attached to an insulative film. A method provides for determining transcapacitance between the first electrode and the second electrode and using the transcapacitance in a model that accounts for a dielectric test piece to determine inversely the properties of the dielectric test piece.
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are plotted in Figure 2(b). By introducing the capacitive annulus, there will be parasitic capacitance between the ground and the capacitive annulus, and the proposed antenna’s input resistance can be increased to 50 ohm in the upper frequency band, which is perfect for matching with the SMA connector. At the same time, the loading capacitive annulus does not change the inherent physical dimension of the sleeve antenna, so the input resistance and reactance in the lower frequency band are almost unchanged. The height (h 4 ) of the capacitive annulus apart from the ground plane and the inner radius (r 4 )
The capacitive accelerometer converts the displacement signal into an electrical signal. Figure 1 shows the layout of SOI-MEMS capacitive z-axis accelerometer. The proof mass is suspended by four compliant beams anchored to a fixed frame. The beam shape physical parameters such as the shape, geometry and material used in this device need to be carefully considered because these properties will influence the stiffness of the beam. Lowering spring stiffness means reducing the natural frequency of the accelerometer. Consequently, the operating bandwidth will also be reduced . In addition, it will lead the beam at handle layer . In order to achieve the desired performance, it is important to ensure that the proof mass is moving without stick and the cross axis sensitivity is lowered. These problems were prevented by designing L-beam to be at centre of mass gravity of the beam correspond to the center of mass, so that the off axis deflection can be minimized.
At the 50% transition points of the input and output waveforms the delay is measured. The performance of the circuit is increased on reducing the gate delay which is directly proportional to the load capacitance, the value of βn and is inversely proportional to the supply voltage. Hence the capacitance of the load is to be reduced while increasing the supply voltage and width of the transistor in order to obtain an optimum delay. But initially we have considered running the load with large capacitances hence we go for a buffer chain with N stages needed.
values are subtracted from each output for amplitude comparison about the origin, as shown in Figures 7.26a and 7.27a. Using the spindle compliance of 0.0436 µm/N (calculated in section 3.5), estimated force values of 230 N and 92 N are obtained from the maximum initial x-forcing and z-forcing displacements of 10 µm and 4 µm, respectively. The excellent consistency between the data sets in these plots verify operation and performance of the x-axis CDS. Though there is a noticeable amplitude difference, the error is small relative to full scale and is likely associated with the slightly increased CDS noise. Figure 7.26b and 7.27b presents frequency response comparisons between CDS and ODS output results for x and z forcing, respectively. The frequency domain results compare quite well, which is expected based on the consistent time domain results. Due to the smaller size and surface area available for electromagnetic actuation in the z-axis, the CDS and ODS measurement amplitudes are significantly reduced.
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The effect of direct radiation from the open end of the microstrip line can be represented by a conductance across the shunt capacitor. In such kind of antenna configuration, the radiation pattern becomes asymmetric due to capacitive loading. To over-come this problem new feeding techniques are design.The two patches can be manufactured on a thin substrate with a thick low-loss substrate, such as air .The gap between the resonant patch and the capacitor patch acts as a series capacitor, thereby offsetting the inductance of the long probe. Once the size of the resonant patch and the thickness of the substrate have been fixed for a certain operating frequency and impedance bandwidth, there are basically two parameters that can be used to control the input impedance of the antenna element[7,9].
In contrast, pulse-emitting Gymnotiformes discharge brief waveforms consisting of a traveling wave along the body (Gymnotidae: Bennett and Grundfest, 1959; Caputi, 1999, Assad et al., 1999; Rodríguez-Cattáneo et al., 2008, 2013; Castelló et al., 2009; Rhamphychtidae: Caputi et al., 1994, Hypoppomidae: Caputi et al., 1998; Stoddard et al., 1999; Waddell et al., 2016). As the near field in the fish neighborhood shows site- and time-dependent amplitude and orientation, any object (either purely resistive or having complex impedance) introduces changes in the strength and time course (i.e. amplitude and phase spectrum) of transcutaneous currents (Pereira and Caputi, 2010). These changes in the local stimulus waveforms are encoded at the primary afferent level (Rodríguez-Cattáneo et al., 2017), allowing object (Aguilera and Caputi, 2003) and individual discrimination (McGregor and Westby, 1992). In fact, within the range 1 – 30 nF, capacitive objects alter the time course of the local transcutaneous currents, provoking a shift in the amplitude spectra [ H ( ω )] to a higher frequency range and also a lag of the lower frequency components of the phase spectra [ θ ( ω ); Aguilera and Caputi, 2003; Rodríguez-Cattáneo et al., 2017). These changes in the local stimulus cause a strong reduction of the latency
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The sLEOD in front of the probe was measured as the voltage drop between the bare tip of a 100 µm diameter insulated copper wire placed against the skin and the carbon base of the stimulus- object cylinder nearest to the ﬁ sh (2 mm separation). The total energy of the stimulus was measured as the root mean squared value of the sLEOD (rms sLEOD). The sLEOD of G. omarorum has three main deflections at the foveal region (called components or phases in other studies and referred to as sV1, sV3 and sV4 according to the nomenclature of Trujillo-Cenóz et al., 1984, extended by Castello et al., 2000 and Aguilera et al., 2001). These deflections were differentially modified by resistive and capacitive loads. When the resistance of the probe object increased, the rms sLEOD decreased and the waveform remained similar with a small decrease in sV4 (Fig. 1B). Besides evoking changes in rms sLEOD, capacitors caused important changes in waveform consisting of reductions of the early negative component (sV1) and increases of the late negative component (sV4; Fig. 1B). These changes were described previously
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Abstract: In order to realize array measurement of water holdup on oil well section, a capacitance-based sensor with planar inter-digital structure is proposed, an integrated detecting module is designed, which converts the measured capacitance value to periodic signal with corresponding frequency, a circuit which extracts signal from current change of power supply is developed. The experimental result shows the above solution has advantages to minimize size sensor, less connections between sensor and circuit boards, strong anti-interference performance and high definition when water holdup is not above 50%, thereby, it has important reference value for developing array capacitance-based log tool for water holdup measurement.
For supercapacitors, a long cycle life is among the most important criteria. Thus an endurance test for P-CMS electrode was conducted using galvanostatic charging-discharging cycles at 0.5 A/g (Fig. 6). After 2000 charge/discharge cycles, the maintaining of specific capacitance is 91% at 0.5 A/g. A typical constant current charge-discharge curve for the P-CMS electrode is displayed inset in Fig. 6. The E-t responses of the charge process reveal almost the mirror image of their corresponding discharge counterparts, and no IR drop is observed, demonstrating excellent electrochemical stability of P-CMS electrode. Taken together, our results demonstrate that the P-CMS electrode gives a large specific capacitance and excellent cycling stability, promising for the development of high- performance supercapactiors.