Effect Of Increase In Number Research Articles

Diversity Analysis of Defect Distribution and Carriers Quantization in Cu 2 ZnSnS 4/Cu2ZnSn(S,Se) 4 Kesterite Quantum Well Solar Cell

Kesterite materials, with a major advantage of direct bandgap and earth abundant material,are popular for low cost and thin film solar cell applications. Despite the popularity, the material fails to achieve significant efficiency due to the emergence of defect states during the growth process. In this paper multiple approaches have been investigated focusing on implementation of Quantum Wells(QW) to enhance the performance of solar cell. QW structure are created using CZTS x Se 1−x and Cu 2 ZnSnS 4 as QW and barrier material layers respectively. The performance evaluation of the QW solar cell is also carried out with the presence of most popular donor-like defect states in a gaussian and tail distribution way. The behavior of the device is investigated in presence of broad range of QWs from 2 to 100QWs to ensure the effect of defects on rise in QWs. The worst case performance of the solar cell is obtained to be efficiency of 9.6% under a high level of defect states. A remarkable observation on the effect of increase in number of QWs and defect states on solar cell parameters solar cell are concluded.

A Combined Numerical and Experimental Investigation on the Effect of Dynamics Characteristics of Metal Expansion Bellows

Metal expansion bellows is an important flexible element used to absorb extension or shrinkage and vibrations of the piping system used in various process applications. Failure of the bellows occurs due to the unpredictable behavior in its convolutions due to severe working conditions. Hence, determination of its dynamic characteristics is of prime importance. To find and analyse dynamic characteristics like axial natural frequencies, modal frequency responses and mode shapes of U-shaped convolution bellows as well as the effect of increase in number of convolutions on the dynamic characteristics. In this paper, analytical, numerical simulation and experimental investigations are performed to find the axial natural frequencies of bellows. Numerical simulation is performed using the mathematical model in MATLAB and modal analysis is performed using ANSYS 15. The deformation and axial natural frequency response of bellows with eight, nine and ten convolutions are obtained by FE analysis for various modes when bellows are subjected to different end conditions. As per the simulation and experimental modal analysis, it is seen that the range of axial natural frequencies with less number of convolutions shows maximum deformation and larger number of convolutions shows minimum deformation. To decrease the axial natural frequency for the given flow rate and to avoid resonance, the number of convolutions of the bellows should be increased for designing the new configuration.

Controlling the aqueous solubility of PNIPAM with hydrophobic molecular units

The effect of co-polymerization of thermo-sensitive polymers with hydrophilic or hydrophobic co-monomers on the LCST and the structure of proximal water remains a fundamental and challenging problem. Here, we employ all-atom molecular dynamics simulations to investigate the aqueous solubility of a thermo-sensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), a hydrophobic polymer polystyrene (PS) and block co-polymers of PNIPAM-co-PS. The simulations of pure oligomers of PNIPAM and PS and their co-polymers are conducted below and above the LCST of PNIPAM to elucidate the effect of increase in number of PS units in PNIPAM-co-PS co-polymers on the coil-to-globule transition of PNIPAM and structure of proximal water. Our simulations suggest that while the LCST of pure PNIPAM oligomers is strongly associated with the structural changes in the proximal water molecules present near PNIPAM, inclusion of PS units disrupts the interactions between PNIPAM and water and promotes the faster dehydration of PNIPAM chains above its LCST. This phenomenon is manifested by a coil-to-globule transition in PNIPAM chains present in PNIPAM-co-PS co-polymers at much shorter times as compared to the pure PNIPAM oligomers. Our results also reveal that with increase in the number of PS units in PNIPAM-co-PS co-polymers the coil-to-globule transition is accelerated.

A Complete Analysis of Channel Estimation and Peak to Average Power Ratio in Wireless Communication Using Discrete Fourier Transform

In wireless communication peak to average power and channel estimation are important parameters which should be considered for efficient communication. At the receiver end, the signal is normally distorted due to channel interference and noise. In this paper we focus on complete analysis of PAPR and channel estimation in wireless communication. For this purpose we use discrete Fourier transform which has many application. In this paper we analyze the effect of increase in number of subcarrier on the performance of PAPR using discrete Fourier transform technique. The paper also describes how discrete Fourier transform can be used to remove the distortion from received signal. Our main motive is to improve the peak to average power ratio with the help of discrete Fourier transform approach. This will improve the power efficiency. All the mathematical equations and simulation for our analysis are done with the help of MATLAB software.

Life time comparison of LED package and the self-ballasted LED lamps by simple linear regression analysis

The energy efficient long-life self-ballasted LED lamps are designed considering the reliability test result of LED package. We also try to predict the lumen maintenance life for the self-ballasted LED lamps because there were a lot of failure mechanisms for a various environment stress. Many studies have investigated the environmental stress effects on LED packages [2,3,4, and 5]. However, comparing to LED package, there is not enough data to study the lumen maintenance life for the self-ballasted LED lamps. IES LM-80-08 is the approved method for measuring lumen maintenance of LED light sources [1]. It suggests using the Arrhenius Equation to calculate the interpolated lumen maintenance life. We followed this method and obtained lumen degradation patterns from three different thermal stresses as indicated in the IEC 62621 standard. Under the three different thermal stresses, the on-off test (30on and 30s off) was conducted on the self-ballasted LED lamps which were made of the same selected LED package (3V, 64mA). The intent of the research isn't to set up a new curve-fit for non-linear lumen degradation pattern. Our research goals are to find methods to compare the lumen degradation pattern of LED package and the self-ballasted LED lamp using simple linear regression analysis. As simple straight linear line is assumed for lumen degradation after ALT testing We found the slope of the mathematical model is easily comparable for three different temperatures and for different number of LED whether it is single or consists of forty or eighty LED. By comparing each values of the slope the effect of increase in number of LED can be shown at each thermal stress. This study is the first step towards the presentation on the lumen maintenance life of the self-ballasted LED lamp on three different temperatures. Additional information must be accumulated in the future to further study on the LED lighting product reliability.

Efficient Performance Analysis of Spectrum Sensing for Cascaded Multihop Network over Nagakami-m Fading Channels

Performance evaluation of spectrum sensing in infrastructure based multihop network is very hard to achieve because of the adverse effects of channel fading. In this paper, performance of a multihop link is studied over Nakagami-m distribution. It provides the exact theoretical methodology for the performance analysis of spectrum sensing by evaluating detection probability. Using a cascaded multihop model, the end-to-end Signal to Noise Ratio (SNR) is given over Nakagami-m distribution. In the analysis, multihop model based on relays are considered over independent and not identically distributed (i.n.i.d) wireless channels. Simulation results show the effect of increase in number of hops on probability of detection for multihop links. Subsequent to the thorough fading severity analysis, it has been accomplished that spectrum hole detection is more crucial at lower SNR values with large number of hops.

Investigation of Flow Mal-distribution in Proton Exchange Membrane Fuel Cell Stack

During the operation of a fuel cell stack, a uniform distribution of reactants from the manifolds to each cell is desired. An uneven flow distribution results in uneven performance between the cells. Though desired, it is difficult to achieve uniform distribution in practice and it is of interest to analyze the nature and magnitude of those undesirable deviations from ideality. In this research works, an attempt is made to experimentally investigate those deviations using pressure drop in a Proton Exchange Membrane Fuel Cell (PEMFC) stack at various stoichiometric flow rates. Fluctuations in pressure drop and effect of increase in number of cells and stochiometric of reactants are analyzed in this works. In addition the impact of flow patterns such as U-type and Z-type are also discussed here.

Analytical Performance Evaluation of Space Time Coded MIMO OFDM Systems Impaired by Fading and Timing Jitter

An analytical approach is presented to determine the impact of time selective fading, timing jitter and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of an orthogonal frequency- division multiplexing (OFDM) system with differential quaternary phase-shift keying (DQPSK), differential phase- shift keying (DPSK) and quaternary phase-shift keying (QPSK) modulation. The expression for the conditional BER conditioned on a given timing error and fading, is derived and the average BER is evaluated. The BER performance results are evaluated for different values of fading and jitter. The performance of the OFDM system in Rayleigh and Rician fading channels is also compared. Analytical approach is also developed to evaluate the BER performance of a quasi-orthogonal- space-time block coded OFDM system having multiple transmitting and single receiving antennas. The analysis is extended for a multiple- input multiple-output (MIMO)-OFDM system using the selection method for combining multiple receiving antennas, which offers significant improvement in the system performance. The effects of increase in number of OFDM subcarriers and increase in Doppler frequency are also investigated.

Cyclohexane oxidation catalyzed by manganese oxide octahedral molecular sieves—Effect of acidity of the catalyst

Oxidation of cyclohexane is an important industrial process, its oxidation products, cyclohexanol and cyclohexanone are raw materials for adipic acid and caprolactam synthesis. Acid exchanged cryptomelane type manganese oxide octahedral molecular sieves (H-K-OMS-2) was used for liquid phase oxidation of cyclohexane with t-butyl hydroperoxide as an oxidant. The H + form of K-OMS-2 was synthesized by ion-exchange of K-OMS-2 with concentrated nitric acid. H-K-OMS-2 has been found to be an efficient catalyst for the oxidation of cyclohexane with a high conversion (∼60%). More than 90% selectivity for cyclohexanol and cyclohexanone was obtained. A turn over number (TON) of 73 was obtained in 24 h at 80 °C and if we consider only contributions of acidic manganese sites then the TON is 287. Effect of increase in number of acid sites of the K-OMS-2 was correlated with the increase in conversion. The reactions were carried out in a semi-batch reactor at 80 °C using acetonitrile as solvent. Effects of solvent, temperature, and amount of t-butyl hydroperoxide on conversion and selectivity were studied.

Comparison of Preimplantation Genetic Diagnosis-Aneuploidy Screening (PGD-AS) With 5 Chromosome Versus 9/10 Chromosome Panels

The purpose of this study was to evaluate the percent of embryos found to be normal using a 5 chromosome panel (PGD5) vs. a 9/10 chromosome panel (PGD9/10) out of total number of embryos biopsied in IVF cycles employing PGD-AS, and the effect of using PGD 5 vs. PGD 9/10 on pregnancy rates. A retrospective analysis of 268 patients undergoing IVF with PGD-AS from September 2003 to May 2004. The medical records were reviewed for age, number of embryos biopsied, number of normal embryos per PGD-AS, number of embryos transferred, and pregnancy outcome including twinning/higher order multiple pregnancies (HOMP) for 4 physicians with similar stimulation protocols. 51 patients met inclusion criteria. Student t-test for two samples and chi-square test were used for statistical analyses. The data for the two groups is shown in Table 1. The mean age, number of total embryos biopsied, and number of embryos transferred were similar between the two groups. The PGD5 group had a higher absolute number and percent of normal embryos diagnosed by PGD (p<0.005, p<0.0001). The pregnancy rate was higher in the PGD5 group, but this did not reach significance. The patients able to conceive (PGD5 or PGD9/10) had a significantly higher number of normal embryos as diagnosed by PGD (4.0 ± 2.2 vs. 2.0 ± 0.97, p<0.0005) and a higher number of embryos transferred (2.5 ± 0.7 vs. 1.9 ± 0.7, p<0.005) as compared to those unable to conceive. One set of quadruplets and two sets of twins were noted in the PGD5 group and one set of quadruplets and three sets of twins in the PGD 9/10 group. Table 1 Tabled 1 A trend towards higher pregnancy rates was noted in the PGD5 group. This may indicate that with an increased number of chromosomes analyzed there is a greater decrease in specificity. A higher number of false-positive abnormal embryos may result in fewer embryos available for transfer. This may lead to transfer of only the remaining available embryos (9/10 chromosome panel) vs. providing a choice to select the best quality embryos for transfer (5 chromosome panel). The comparison of pregnant to non-pregnant women showed a higher number of normal embryos available on day of transfer and a higher number of embryos transferred (perhaps with higher quality as well). The implantation rate was higher in the PGD5 group. This confirms the higher quality of embryos transferred using the 5 chromosome panel vs. the 9/10 chromosome panel. The twinning /HOMP rate was similar in the PGD5 vs. the PGD9/10 group, failing to show an adverse effect of increase in number of embryos transferred. Therefore, PGD using a 9/10 chromosome panel offers little added value over a 5 chromosome panel with a potential adverse effect on pregnancy rates.

Effect of Sm3+ concentration on electroluminescence excitation mechanism in (Zn, Cd) S phosphors

(Zn, Cd)S phosphors activated with varying concentrations of Sm3+ have been prepared in argon atmosphere, and their voltage dependence of EL-brightness, current-voltage characteristics and SEM measurements have been carried out. The nature of variation of EL-brightness with voltage is found to depend on Sm3+ concentration. The result is interpreted as an effect of increase in number and effectiveness of Mott-Schottky type potential barriers which probably exist at the grain boundaries.