Power Vector Research Articles

LVRT capability based on P‐V curve fitting under partial shading conditions

The new generation of photovoltaic (PV) systems represents higher sustainability during grid faults thanks to increased ancillary services, such as low voltage ride-through (LVRT) capability used when the PV system is subjected to voltage sag. Unlike previously presented strategies that just dealt with voltage sag problem under uniform radiation conditions, in this study, a new control strategy implementing LVRT capability during low-voltage faults under partial shading conditions is proposed. First, radiation levels are estimated by using the least-squares curve fitting (LSCF) algorithm. Second, the voltage/current of maximum power points (MPPs) and minimum power points are calculated. Also, the corresponding algebraic function for the (Power - Voltage) P-V curve is extracted using only PV voltage and power vectors. Finally, under partial shading conditions, the moving operating point to the right side of MPP is well-achieved through a power proportional-integral controller. To validate the effectiveness of the proposed control strategy, simulations and experiments are conducted on PV systems. The simulation and experimental results and the comparison made between this algorithm's performance and other methods confirm that the proposed algorithm outperforms other methods in terms of high accuracy, fast dynamic and low oscillations in different partial shading conditions and with different radiations.

Achievable Computation Rate in NOMA-Based Wireless-Powered Networks Assisted by Multiple Fog Servers

This article investigates a multifog server (FS)-assisted nonorthogonal multiple access (NOMA)-based wireless powered network, where an energy-limited wireless device (WD) first harvests energy from a power transmitter (PT) and multiple helping FSs and then uses the harvested energy to partially offload its computing task to the FSs with NOMA for computing. To explore the WD's performance limit in terms of achievable computation rate, an optimization problem is formulated by jointly optimizing the time assignment, the power allocation, and the computation frequency under multiple system constraints. Since the problem is nonconvex with no known solution, an efficient solution approach is designed to achieve the ε-optimal solution, in which the transmit power vector and the computation frequency are jointly optimized with fixed-time assignment, and then, a golden section search (GSS)-based algorithm is designed to find the optimal time assignment. For the case when the FS is with sufficiently strong computation capability, some semiclosed-form results are derived. Numerous results show that our proposed design achieves much higher computation rate than benchmark schemes. Moreover, with the increment of the helping FSs, the achievable computation rate increases while the increasing rate is decreased. Besides, by employing NOMA, the WD's computation rate is also improved compared with orthogonal multiple access (OMA)-based scheme. Additionally, in such a system, with nonlinear energy harvesting (EH) model adopted, the more the helping FSs are deployed, the more the performance loss caused by the traditional linear EH model can be reduced.

Evaluation of a Portable Wavefront Aberrometer for Community Screening Refraction in the Elderly.

The SVOne may prove useful to quickly and easily assess refractive correction needs in community screenings and low-resource settings, but not all subjects were testable with the device. This study aimed to compare the SVOne handheld, smartphone-based wavefront aberrometer with a tabletop autorefractor in identifying refractive errors in elderly subjects. Participants 50 years or older at community eye screenings with visual acuity worse than 20/40 in either eye underwent autorefraction followed by two SVOne trials. Power vectors of right eye data were analyzed. Of 84 subjects who underwent autorefraction, 67 (79.8%) were successfully autorefracted with the SVOne, of whom 82.1% (55/67) had a successful repeat reading. Mean M (spherical equivalent) values from tabletop and handheld autorefraction were -0.21 D (95% confidence interval [CI], -0.71 to +0.29 D) and -0.29 D (95% CI, -0.79 to +0.21 D), respectively (P > .05). Mean astigmatism values from tabletop and handheld devices were +1.06 D (95% CI, 0.87 to 1.26 D) and +1.21 D (95% CI, 0.99 to 1.43 D), respectively (P > .05). Intraclass correlation coefficients between devices were 0.95 (95% CI, 0.93 to 0.97) for M, 0.78 (95% CI, 0.66 to 0.86) for J0, and 0.45 (95% CI, 0.24 to 0.63) for J45 (P < .05 for all). Excellent test-retest correlation between SVOne measurements was noted for M (Pearson correlation [r] = 0.96; P < .05), but a weaker correlation was noted for J0 and J45 (r = 0.67 and r = 0.63 [P < .05 for both], respectively). The SVOne provided strong agreement for M, with the majority of readings within ±1.00 D of each other, when compared with the tabletop autorefractor. A weaker but still good correlation was noted for astigmatism. Similar findings were noted when assessing repeatability.

HRM in Brazil: an institutional approach

PurposeThe purpose of this work is to comparatively study human resources management (HRM) areas in Brazil, at the national level, analyzing how companies considered labor market and labor relations aspects when building their strategies and when configuring people management models in place in the country (2014–2019), based on local conditions.Design/methodology/approachThe subject was approached through qualitative analysis, encompassing document survey, systematic literature review, specialists' panel discussions, eight focus groups (43 human resources [HR] managers), interviews (16 union members), applying institutional approach to people management.FindingsIn regards to labor market and unions, HR areas faced different conditions across Brazilian regions. They have dealt with those influences on their strategic and quotidian decisions in an unstructured fashion. HR areas remain constructed as traditional, adjuvant and far from strategic level. In the institutionalization process – normative isomorphism – a professional HR jargon use was identified. HR areas usually act in collective bargaining, resorting to specialized professionals or consulting companies. During the economic crisis, HR professionals' attitude had a reactive nature, responding to organizations leadership, with little dedication to the emerging context.Practical implicationsThis work enables important players like HR managers, union members and specialists in public policies to interpret the institutionalization phenomena of practices related to management, labor market and labor relations in the country.Social implicationsUnderstanding the effects of the relations among state, companies and unions allows the different power vectors, acting upon the institutionalization process of people management areas in the Brazilian case, to be outlined.Originality/valueThis study applies the institutional approach to understand the economic and social heterogeneity affecting organizations in Brazil. It enhances the knowledge on HRM areas scope and their articulation toward labor market and relations.

Off-grid DOA estimation through variational Bayesian inference in colored noise environment

This paper provides a direction-of-arrival (DOA) estimation method based on sparse Bayesian learning for a colored noise environment. In this method, the harmonic noise model is absorbed into the covariance matrix model to express the noise objectively. As such, the covariance matrix is parameterized with the signal powers and noise parameters. Given that the existing Bayesian models cannot be directly used for this covariance matrix model, this paper establishes a new probabilistic model. Different priors are assigned for signal power vector and noise parameter vector since signal power vector is sparse but noise parameter vector is not. Based on this probabilistic model, the variational Bayesian inference is applied to estimate signal powers and noise parameters. Moreover, first-order Taylor series expansion is applied to approximate the virtual steering vector as a function of the grid error between the true DOA and the closest grid point. Grid error is estimated in the Bayesian framework and applied to modify the grid, thus alleviating basis mismatch. Simulation results prove that the proposed method achieves high estimation accuracy with a mild computational complexity in a colored noise environment.

Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors?

PurposeThe purpose of this study was to determine the accuracy and repeatability of refractive errors obtained using three autorefractors based on different measurement principles, vis-à-vis, gold-standard retinoscopy.MethodologyAccuracy of noncycloplegic, sphero-cylindrical refractive error of 234 eyes was obtained using the rotary prism-based RM-8900 closed-field autorefractor, photorefraction based Spot vision screener, wavefront aberrometry based E-see, and streak retinoscopy by four different examiners, masked to the results of each other. Intersession repeatability of autorefractors was determined by repeat measurements in a subset of 40 subjects.ResultsRetinoscopy values of M, J0, and J45 power vectors for the cohort ranged from −10.2 to 8 D, −1.4 to 1.8 D, and −0.9 to 1.2 D, respectively. Across autorefractors, the interequipment bias of M and J0 power vectors were statistically insignificant (< ±0.5 D; P > 0.05) but the corresponding limits of agreement were ±2.5 and ±1 D, respectively, without any trend across instruments or the patient's age (P > 0.5). Repeatability of M and J0 power vectors were ±0.75 D and ±0.40 D, respectively, across autorefractors. The range of J45 power vector was too narrow for any meaningful analysis.ConclusionsRefractive errors measured using autorefractors operating on different principles show minimal bias and good short-term repeatability but relatively large agreement limits, vis-à-vis, retinoscopy. Among them, the wavefront aberrometry based E-see autorefractor performs relatively better in all measurement parameters evaluated here.Translational RelevanceAlthough autorefractor estimates of noncycloplegic refractive error appears independent of their measurement principle, their relatively poor agreement with gold-standard retinoscopy warrants caution while used for screening and quantification of refractive errors.

Joint Beamforming and Power Allocation for Multiuser MISO Broadcast Channel SWIPT Employing OFDM

Resource allocation strategies for simultaneous wireless information and power transfer (SWIPT) employing orthogonal frequency division multiplexing (OFDM) typically rely on subcarrier assignment for multiple access. For information transfer, however, subcarrier assignment is only sum-rate optimal when the network is interference limited; otherwise, it is optimal to reuse subcarriers. Beamforming-based space-division multiple access (SDMA) is a multiple access technique that enables subcarrier reuse by managing interference. Although beamforming is considered a key SWIPT component, OFDM-based SWIPT has yet to utilize beamforming for SDMA. As such, this paper seeks to develop a low-complexity resource allocation strategy to jointly allocate power and design beamforming vectors for an OFDM-based multiuser (MU) multiple-input single-output (MISO) broadcast channel (BC) SWIPT system capable of utilizing SDMA. To this end, a non-convex optimization problem is formulated in which a weighted sum of user data rates is maximized subject to meeting receive and transmit power constraints. The time-sharing property of multicarrier systems is observed to justify utilizing Lagrangian decomposition despite the non-convexity. Whereas previous SWIPT research used Lagrangian decomposition to simplify subcarrier assignment, this paper instead uses it to enable SDMA through beamforming. Beamforming is achieved via a medium access channel (MAC)-BC duality, which enables a closed-form solution for the beamforming vectors given the dual MAC power allocation. The dual MAC power allocation is approximated using a successive convex approximation (SCA) technique. The result is a resource allocation algorithm that provides close-to-optimal performance with low computational complexity.

Surgical Treatment of Epiblepharon Effectively Alleviates Keratopathy but Not Astigmatism: A Case-Control Study Utilizing Vector Analysis in East Asian Children.

Purpose To identify an appropriate surgical indication of epiblepharon by comparing keratopathy and astigmatism outcomes after surgical and medical treatments for epiblepharon in Asian children. Methods Children diagnosed with epiblepharon (n = 82, age 5.93 ± 2.76 years) with >6 months of follow-up were enrolled. The clinical presentations and cycloplegic refractive status at the baseline and 3 and 6 months after treatment were compared between surgical (91 eyes from 47 children) and nonsurgical (67 eyes from 35 children) groups. The refractive and keratometric astigmatism at each time point were evaluated with vector analysis methods. For Thibos and Horner's method, the astigmatic power vector was decomposed into horizontal and oblique meridians (J0 and J45). However, the treatment-induced astigmatism (TIA) vectors were calculated by Alpins' method and depicted by the AstigMATIC software. Results In the surgical and nonsurgical groups, the baseline astigmatism magnitude was similar (2.22 ± 1.39 and 2.26 ± 1.46 D, p = 0.87). The rate of complete resolution of keratopathy at 6 months was 71.4% and 11.5%. The astigmatism magnitude in the surgical group differed among baseline and 3 months (2.25 ± 1.23 D) and 6 months postoperatively (1.97 ± 1.28 D) (p = 0.001). Power vector analyses confirmed a nuanced against-the-rule shift in the surgical group. This trend was especially observed in the subgroup of baseline astigmatism >2.0 D. However, the difference in the astigmatism magnitude between surgical and nonsurgical groups, even in highly astigmatic children, was not significant at 6 months. Conclusions The improvement of keratopathy in the surgical group was greater than that in the nonsurgical group in consideration of the more advanced severity in the surgery group at baseline. Decreased with-the-rule astigmatism can be observed at 6 months postoperatively, particularly among those with greater baseline astigmatism. However, the amount of change is small, and the outcome does not differ significantly from the nonsurgical treatment. Therefore, surgical indications should majorly base on the severity of symptoms and keratopathy.

DQ Impedance Stability Analysis for the Power-Controlled Grid-Connected Inverter

For a grid-connected inverter requiring the ac voltage magnitude and the active power control, both vector control and power synchronization control can be applied. The stability comparison based on the dq impedance stability analysis between both control are carried out via three factors including the grid impedance, the inner current loop and the virtual impedance. The dq impedances of the inverter based on both control are derived. The determinant of the impedance ratio matrix is used for the stability analysis. The bode plot of the grid impedance and the inverter impedance are present to assist the stability analysis and explain their interactions. It is found that increasing the grid impedance and the cut-off frequency of the current loop stabilize the inverter with the power synchronization control, which is converse to the vector control. Furthermore, the inverter with the power synchronization control may suffer the instabilities when connecting to a strong grid. The virtual inductor and resistor are proposed to enhance the stability for the vector control and the power synchronization control respectively. The simulation validation using Matlab/Simulink is performed.

Подавление узкополосных стационарных помех в телеметрическом комплексе на основе автокомпенсатора с удаленными каналами.

The problem of combating stationary interference in the areas of operation of ground-based telemetry systems is considered. One of the most annoying types of interference is high-power narrowband TV interference. They are emitted from television towers and their position is known in advance. A solution to this problem is proposed by using a multichannel auto-compensator with a non-standard arrangement of compensation channels. An analytical solution is obtained for the optimal weight vector of the auto-compensator of interference, based on the method of power vectors. This method does not require direct inversion of the interference correlation matrix. The computational complexity of the proposed method is estimated and it is shown that it has a much lower computational complexity compared to the method of direct inversion of the interference correlation matrix. The results of numerical simulation of the interference suppression coefficient are presented. Its effectiveness has been shown.

Divergence zero quaternionic vector fields and Hamming graphs

We give a possible extension of the definition of quaternionic power series, partial derivatives and vector fields in the case of two (and then several) non commutative (quaternionic) variables. In this setting we also investigate the problem of describing zero functions which are not null functions in the formal sense. A connection between an analytic condition and a graph theoretic property of a subgraph of a Hamming graph is shown, namely the condition that polynomial vector field has formal divergence zero is equivalent to connectedness of subgraphs of Hamming graphs H ( d , 2) . We prove that monomials in variables z and w are always linearly independent as functions only in bidegrees ( p , 0), ( p , 1), (0, q ), (1, q ) and (2, 2).

Unbalanced Source Detection in Power Distribution Networks by Negative Sequence Apparent Powers

Distribution network unbalanced operation is among crucial power quality concerns. Detecting the unbalance sources and their contribution to the network total unbalance with high precision is a prerequisite to alleviate this challenge. To do so, this letter proposes a new method based on load and branch negative sequence apparent power vectors. The inner product decomposition algorithm is employed to specify the contribution of each downstream unbalanced load on a given branch or node unbalance index. Accordingly, the unbalanced loads compensating for the others can also be discriminated. Referring to simulations, the proposed method outperforms the existing techniques in terms of efficiency and accuracy.

Accuracy of WASCA Aberrometer Refraction Compared to Manifest Refraction and Cycloplegic Refraction in Hyperopia Measurement.

PurposeTo explore the agreement between the wavefront supported custom ablation (WASCA) aberrometer and manifest refraction (MR) and cycloplegic refraction (CR) in hyperopia testing.MethodsNinety eyes of 90 hyperopic patients (spherical equivalent ≥ +0.5 D) were evaluated; MR, CR, and WASCA refraction (WR) were performed consecutively. Analysis pupil size was 6.0 mm in WASCA measurement using the Seidel method. The conventional notation was transferred into vector components for analysis, i.e., spherical equivalent (M) and two cross-cylinders at axis 0° (J0) and axis 45° (J45). Bland-Altman plots were used to test the agreement between the two measurements.ResultsThe mean Ms obtained with MR and CR were 3.23 ± 1.74 D and 4.04 ± 2.04 D, respectively (P < 0.001), and the correlation was high (r = 0.90, P < 0.001). The WR was highly correlated with MR and CR in terms of M (r = 0.89, 0.87), but not significantly correlated in J0 and J45. The total dioptric power vector error was 0.18 ± 1.00 D between WR and MR and −0.64 ± 1.03 D between WR and CR. The limits of agreement of all vector components were beyond ± 1.0 D. With hyperopia level increase, WR tended to overestimate MR (P = 0.04), whereas WR always underestimated CR.ConclusionsWASCA could act as a reference of subjective refraction in hyperopia measurement, the exchangeability is not fully applicable.Translational RelevanceWASCA can provide an alternative for objective refraction in hyperopia measurement.

Longitudinal Analysis of Refractive Errors in Premature Children during the First Three Years of Life

ABSTRACT Purpose To examine the longitudinal behavior of refractive errors in both retinopathy of prematurity (ROP) and non-ROP screened premature children during the first three years of life. Methods This retrospective cohort included premature children (less than 37 weeks gestational age) born between 10/2011 and 8/2013 with ≥ two cycloplegic refractions. Cycloplegic refractions were converted into power vectors: M (spherical equivalent), J0 [positive for with-the-rule (WTR) and negative for against-the-rule (ATR) astigmatism], and J 45 (oblique astigmatism). Each power vector component was fitted by multilevel mixed-effects linear regression models; the mean change over time was analyzed. Results Mean J0 was 0.59 (95% CI 0.53–0.66) at six months and 0.29 (95% CI 0.19–0.39) at 18 months; afterward, the change was <0.1 per year. J0 decreased −0.32 (0.64 diopters) over three years. When analyzed in one-year increments, the mean change in J0 and M was lowest at 24 months. M decreased 1.13 diopters over three years. Conclusion WTR astigmatism and spherical equivalent decreased over the first three years of life. WTR astigmatism accounted for the majority of amblyopogenic refractive errors. The change in J0 leveled after 18 months and the lowest rate of change was at 24 months in J0 and M, thus it may be appropriate to screen this high-risk population around 18–24 months.

Projected Kernel Least Mean $p$ -Power Algorithm: Convergence Analyses and Modifications

Sparsified kernel adaptive filters (SKAFs) is an attractive filtering solution with low memory and computational complexity. Most of existing SKAFs are based on the mean square error (MSE) criterion under Gaussian noise assumption for its simplicity and convenience. When the assumption deviates largely from the underlying truth, the performance of these methods could degrade significantly. In this paper, we propose a novel SKAF, named as projected kernel least mean $p$ -power algorithm (PKLMP), based on the mean $p$ -power error (MPE) criterion and vector projection (VP) method. We provide convergence analyses in terms of the stead-state MSE, based on a Taylor expansion method, and derive the lower and upper bounds for the steady-state excess MSE. We also conduct mean convergence analysis for PKLMP, and derive convergence conditions. To exploit the information in the desired outputs, we further derive a modified PKLMP by smoothing the desired signal. Finally, a simple and effective online variable kernel centers strategy is proposed to improve the filtering performance of the proposed KAFs. Simulation results under a static function estimation, a chaotic time-series prediction, and two real-world time-series predictions are conducted and validate the effectiveness of the proposed PKLMP algorithms.

Corneal and Ocular Residual Astigmatism in School-Age Children.

Purpose:To determine the distribution of residual and corneal astigmatism (CA) in children aged 6–18 years and their relationship with age, sex, spherical equivalent, and biometric parameters.Methods:In this cross-sectional study, multi-stage stratified cluster sampling was done to select students from Dezful, a city in Southwestern Iran. Examinations included the measurement of visual acuity with and without optical correction, refraction with and without cycloplegia, and biometry using the Biograph (Lenstar, Germany). The main outcomes in this report were corneal and residual astigmatism. The CA was measured by Biograph (difference between k1 and k2), and residual astigmatism was calculated using Alpine method. The power vector method was applied to analyze the data of astigmatism.Results:Of 864 students that were selected, 683 (79.1%) participated in the study. The mean residual and CA were -0.84 diopter (D) and -0.85 D, respectively. According to the results of J0 and J45 vectors, residual astigmatism was -0.33 D and 0.04 D, and CA was 0.38 D and 0.01 D, respectively. With-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism were seen in 3.4%, 66.8%, and 4.5% of the children with residual astigmatism and 67.94%, 1.3%, and 1.5% of the children with CA. Residual astigmatism decreased with an increase in spherical refractive error, whereas CA increased with an increase in spherical refractive error.Conclusion:The results of the present study showed a high prevalence and amount of residual astigmatism with ATR pattern among the 6–18-year-old population and the compensatory effect of this type of astigmatism on CA that mostly followed a WTR pattern.

Agreement of wavefront-based refraction, dry and cycloplegic autorefraction with subjective refraction

PurposeTo evaluate the agreement of dry, and cycloplegic autorefraction and wavefront-based refraction with subjective refraction. Method83 subjects aged 19–57 years were included in this cross-sectional study. Refractive status was determined using four methods including subjective refraction, wavefront-based refraction, dry and cycloplegic autorefraction. Refractive data were recorded as sphere, cylinder and spherical equivalent (SE). Power vector components were used to compare the astigmatism obtained using the different methods of refraction. ResultsThe more negative spherical, cylindrical and SE components were obtained using dry autorefraction, wavefront-based refraction and dry autorefraction, respectively. The less negative spherical, cylindrical and SE components were obtained using cycloplegic autorefraction, subjective refraction and cycloplegic autorefraction, respectively. Considering the spherical component, there was a statistically significant hyperopic shift (0.12 ± 0.29 D, p = 0.001) with cycloplegic autorefraction and a significant myopic shift (−0.17 ± 0.32 D, p < 0.001) with dry autorefraction compared to subjective refraction, while the difference between wavefront-based and subjective refraction was not significant statistically (p = 0.145). The calculated cylindrical component using subjective refraction showed statistically significant difference with dry auto-refraction (p < 0.001), cycloplegic auto-refraction (p = 0.041) and wavefront refraction (p < 0.001). The highest correlation with subjective refraction in sphere, cylinder and SE was observed for cycloplegic auto-refraction (rs = 0.967), dry auto-refraction (rs = 0.983) and cycloplegic auto-refraction (rs = 0.982), respectively. ConclusionsAs subjective refraction is gold standard in our study, sphere in cycloplegic auto-refraction and astigmatism in dry auto-refraction showed better agreement and correlation.

Comparative analysis of anterior corneal curvature and astigmatism measurements obtained with three different devices

BackgroundThe objective of this study was to compare the central corneal curvature and astigmatism measurements obtained with three different systems in healthy eyes and to assess the level of interchangeability between them.MethodsThis was a comparative study examining 30 healthy eyes of 30 patients (age 15–53-years). A complete eye examination was performed in all cases including analysis of anterior corneal curvature and astigmatism with three devices: the colour‐LED topography system Cassini (i‐Optics) (CAS), the Scheimpflug‐based system Pentacam (Oculus Optikgeräte) (PTC) and the optical biometer IOL‐Master 500 (Carl Zeiss Meditec) (IOLM). Differences between devices in terms of curvature in the flattest (flat K) and steepest meridians (steep K) as well as in the magnitude (AST) and power vector components of astigmatism (J0 and J45) were evaluated. The interchangeability between devices was evaluated with the Bland–Altman method.ResultsStatistically significant differences between devices were found in steep K and flat K (p < 0.001). No statistically significant differences between devices were found in AST (p = 0.057) and J0 power vector (p = 0.185). However, differences between devices in J45 did reach statistical significance (p = 0.039). Ranges of agreement for curvature measures ranged from 0.123 (flat K, CAS‐PTC) to 0.165-mm (steep K, CAS‐PTC). Ranges for the magnitude of astigmatism were 0.868, 1.059 and 0.739 D in CAS‐IOLM, PTC‐IOLM and CAS‐PTC comparisons, respectively. For J0 and J45, ranges of agreement were below 0.522 D.ConclusionsMeasurements of central corneal curvature and astigmatism obtained with the three devices evaluated cannot be used interchangeably.

Dynamic MODCOD and power allocation in DVB-S2: a hybrid intelligent approach

Adaptive communication for is one of the hottest areas of research in the telecommunication systems including wireless broadcast systems. This is primarily accomplished for sake of boosting the transmission throughput with enhanced quality of service and ideal link utilization. In adaptive communication, various radio transmission parameters like modulation symbol, code-rate and power etc. are carefully chosen according to the erratic channel state information on the link. Digital video broadcast—second generation (DVB-S2) has an inbuilt support for adaptive coding and modulation (ACM). However, power adaptation is still a necessity because of power constraint in downlink where satellite has a limited power bank. Moreover, different downlinks have distinct transmit power requirements due to diverse ambient on earth receivers like rainy, foggy, stormy and with clear sky etc., hence flat transmit power distribution among all the ground receivers may not be a good idea at all. To utilize the ACM feature in DVB-S2 and to additionally adapt power, in this paper, an adaptive modulation, coding (MODCOD) and power scheme is proposed. By investigating a fuzzy system and differential evolution algorithm, to select the set of MODCODs and optimum power vector, respectively, for the next transmission interval. From the simulation results it is apparent that the proposed scheme is promising in terms of efficient link and transmit power utilization as well as quality of service compared to the schemes in the literature with flat power distribution.

Characteristics of component matrices chosen for toric lens powers in symmetric dioptric power space

Real distinct principal powers and corresponding perpendicular meridians of a lens or surface combine as factors of a 2×2 power matrix for calculation. A scalar matrix that represents the nearest sphere power component, may be extracted from this. Non-spherical or astigmatic matrix power component(s) remain. The purpose of this paper is to analyse the contribution that astigmatic components in two planes make to the lens power. These basic power members of the set of matrix basic components provide the preferred meridians as they combine linearly to complete the power matrix of a lens or surface. Essentially invertible independent matrices make for symmetric basic components. The maximum number of mutually orthogonal matrices in a vector space of finite dimension form a basis for that space. Properties of basic matrices are latent in the use of optometric power vectors. This paper attempts to make the case for the explicit mention of orthogonal bases of matrices in order to support calculations of power.