Paediatric intraocular lens implants: accuracy of lens power calculations.
O'Gallagher, M K; Lagan, M A; Mulholland, C P; Parker, M; McGinnity, G; McLoone, E M
2016-09-01
PurposeThis study aims to evaluate the accuracy of lens prediction formulae on a paediatric population.MethodsA retrospective case-note review was undertaken of patients under 8 years old who underwent cataract surgery with primary lens implantation in a regional referral centre for paediatric ophthalmology, excluding those whose procedure was secondary to trauma. Biometric and refractive data were analysed for 43 eyes, including prediction errors (PE). Statistical measures used included mean absolute error (MAE), median absolute error (MedAE), Student's t-test and Lin's correlation coefficient.ResultsThe mean PE using the SRK-II formula was +0.96 D (range -2.47D to +2.41 D, SD 1.33 D, MAE 1.38 D, MedAE 1.55, n=15). The mean PE was smaller using SRK/T (-0.18 D, range -3.25 D to +3.95 D, SD 1.70 D, MAE 1.30 D, MedAE 1.24, n=27). We performed an analysis of the biometry data using four different formula (Hoffer Q, Holladay 1, SRK-II and SRK/T). Hoffer Q showed a smaller MedAE than other formulae but also a myopic bias.ConclusionOur clinical data suggest SRK/T was more accurate in predicting post-operative refraction in this cohort of paediatric patients undergoing cataract surgery. Hoffer Q may have improved accuracy further.
What Factors Affect Intraocular Lens Power Calculation?
Fayette, Rose M; Cakiner-Egilmez, Tulay
2015-01-01
Obtaining precise postoperative target refraction is of utmost importance in today's modern cataract and refractive surgery. Emerging literature has linked postoperative surprises to corneal curvature, axial length, and estimation of the effective IOL position. As demonstrated in this case presentation, an inaccuracy in the axial length measurement can lead to a myopic surprise. A review of the literature has demonstrated that prevention of postoperative refractive surprises requires highly experienced nurses, technicians, and/ or biometrists to take meticulous measurements using biometry devices, and surgeons to re-evaluate these calculations prior to the surgery.
Glišić Selimir
2015-12-01
Full Text Available Cataract surgery and intraocular lens power calculation is challenging in patients with anterior megalophthalmos and cataract, with postoperative refractive surprise frequently reported. Deep anterior chamber in these patients substantially influence effective lens position. To minimize possibility of refractive surprise, we used Haigis formula that takes into account anterior chamber depth in the lens power calculation for our patient. Cataract was managed by phakoemulsification with standard intraocular lens implanted in the capsular bag. Postoperatively, satisfying refractive result was achieved and refractive surprise was avoided.
Comparison of two optical biometers in intraocular lens power calculation
Sheng Hui
2014-01-01
Full Text Available Aims: To compare the consistency and accuracy in ocular biometric measurements and intraocular lens (IOL power calculations using the new optical low-coherence reflectometry and partial coherence interferometry. Subjects and Methods: The clinical data of 122 eyes of 72 cataract patients were analyzed retrospectively. All patients were measured with a new optical low-coherence reflectometry system, using the LENSTAR LS 900 (Haag Streit AG/ALLEGRO BioGraph biometer (Wavelight., AG, and partial coherence interferometry (IOLMaster V.5.4 [Carl Zeiss., Meditec, AG] before phacoemulsification and IOL implantation. Repeated measurements, as recommended by the manufacturers, were performed by the same examiner with both devices. Using the parameters of axial length (AL, corneal refractive power (K1 and K2, and anterior chamber depth (ACD, power calculations for AcrySof SA60AT IOL were compared between the two devices using five formulas. The target was emmetropia. Statistical analysis was performed using Statistical Package for the Social Sciences software (SPSS 13.0 with t-test as well as linear regression. A P value < 0.05 was considered to be statistically significant. Results: The mean age of 72 cataract patients was 64.6 years ± 13.4 [standard deviation]. Of the biometry parameters, K1, K2 and [K1 + K2]/2 values were significantly different between the two devices (mean difference, K1: −0.05 ± 0.21 D; K2: −0.12 ± 0.20 D; [K1 + K2]/2: −0.08 ± 0.14 D. P <0.05. There was no statistically significant difference in AL and ACD between the two devices. The correlations of AL, K1, K2, and ACD between the two devices were high. The mean differences in IOL power calculations using the five formulas were not statistically significant between the two devices. Conclusions: New optical low-coherence reflectometry provides measurements that correlate well to those of partial coherence interferometry, thus it is a precise device that can be used for the
Helaly, Hany A.; El-Hifnawy, Mohammad A. M.; Shaheen, Mohamed Shafik; Abou El-Kheir, Amr F.
2016-01-01
Purpose: To evaluate the accuracy of corneal power measurements for intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK). Methods: The study evaluated 45 eyes with a history of myopic LASIK. Corneal power was measured using manual keratometry, automated keratometry, optical biometry, and Scheimflug tomography. Different hypothetical IOL power calculation formulas were performed for each case. Results: The steepest mean K value was measured with manual keratometry (37.48 ± 2.86 D) followed by automated keratometry (37.31 ± 2.83 D) then optical biometry (37.06 ± 2.98 D) followed by Scheimflug tomography (36.55 ± 3.08). None of the K values generated by Scheimflug tomography were steeper than the measurements from the other 3 instruments. Using equivalent K reading (EKR) 4 mm with the Double-K SRK/T formula, the refractive outcome generated 97.8% of cases within ± 2 D, 80.0% of cases within ± 1 D, and 42.2% of cases within ± 0.5 D. The best combination of formulas was “Shammas-PL + Double-K SRK/T formula using EKR 4 mm.” Conclusion: Scheimflug tomography imaging using the Holladay EKR 4 mm improved the accuracy of IOL power calculation in post-LASIK eyes. The best option is a combination of formulas. We recommended the use the combined “Shammas-PL ± Double-K SRK/T formula using EKR 4 mm”h for optical outcomes. PMID:26957851
Scheimpflug corneal power measurements for intraocular lens power calculation in cataract surgery.
Saad, Elie; Shammas, Maya C; Shammas, H John
2013-09-01
To compare the keratometric (K) readings from the Pentacam-HR (High Resolution) unit with the automated K values from the IOLMaster keratometer (KIOLM), and to evaluate them in the commonly used intraocular lens (IOL) power calculation formulas for routine cataract surgery. Prospective, comparative observational study. setting: Private practice, Lynwood, California. study population: Fifty cataractous eyes scheduled for surgery between July and August 2012. observation procedure: The K readings from the Pentacam-HR unit taken at the 2-, 3-, 4-, and 5-mm zones and the 2-, 3-, 4-, and 5-mm rings, respectively, from 3 different maps: sagittal corneal front (KF), true net power (KTNP), and total refractive power (KRP) are compared with KIOLM. IOL power calculations were performed with each of the 25 sets of K readings. main outcome measures: The IOL prediction median absolute error (MedAE) obtained with each measurement. KF averaged 0.03-0.13 diopter (D) higher than KIOLM (P > .05), KTNP averaged 1.16-1.21 D lower than KIOLM (P > .001), and KRP averaged 0.23-0.72 D lower than KIOLM (P > .001), with large variations in the measurements. The MedAE obtained with the different Pentacam K readings ranged from 0.44-0.64 D vs 0.52 D obtained with KIOLM (P > .05). MedAE was lower in all categories when the pupil was 3 mm or smaller. The Pentacam KF values were the closest to KIOLM and the KF readings from the 2-mm ring yielded the best results for IOL power calculation. Copyright © 2013 Elsevier Inc. All rights reserved.
Accuracy of intraocular lens power calculations using the Zeiss IOL master. A prospective study.
Verhulst, E; Vrijghem, J C
2001-01-01
Partial Coherence Interferometry (PCI) is a fast, noncontact method to calculate lens implant power for cataract surgery. It has been reported as a potentially more accurate method than ultrasound biometry. Prospective study of the refractive outcomes of a consecutive series of patients undergoing phacoemulsification surgery with preoperative biometry by both ultrasound A-scan and PCI. A series of 50 eyes of 35 patients underwent small-incision phacoemulsification cataract surgery and lens implantation by one single surgeon. All patients had preoperative biometry performed by both ultrasound using the Sonomed and IOL Master optical biometry. The IOL Master results were included in the SRK II formula to calculate the lens implant power. Postoperative refractive assessment was performed 4 weeks after surgery. The mean difference in axial length between ultrasound and optical biometry was 0.2 mm. The IOL Master measures a longer axial length. The mean keratometric power using the Javal instrument was 43.4 D and for the Zeiss IOL Master it was 42.9 D. At the week 4 postsurgery assessment, the overall refractive outcome was in the range of +/- 1D. Five patients were unable to undergo PCI biometry due to the density of cataract. Intraocular lens power calculations using the Zeiss IOL Master are easy to perform and result in excellent refractive outcomes. A-scan biometry is still needed in case of mature cataract.
Davison JA
2015-08-01
Full Text Available James A Davison,1 Richard Potvin21Wolfe Eye Clinic, Marshalltown, IA, USA; 2Science in Vision, Akron, NY, USAPurpose: To determine whether the total corneal refractive power (TCRP value, which is based on measurement of both anterior and posterior corneal astigmatism, is effective for toric intraocular lens (IOL calculation with AcrySof® Toric IOLsPatients and methods: A consecutive series of cataract surgery cases with AcrySof toric IOL implantation was studied retrospectively. The IOLMaster® was used for calculation of IOL sphere, the Pentacam® TCRP 3.0 mm apex/ring value was used as the keratometry input to the AcrySof Toric IOL Calculator and the VERION™ Digital Marker for surgical orientation. The keratometry readings from the VERION reference unit were recorded but not used in the actual calculation. Vector differences between expected and actual residual refractive cylinder were calculated and compared to simulated vector errors using the collected VERION keratometry data.Results: In total, 83 eyes of 56 patients were analyzed. Residual refractive cylinder was 0.25 D or lower in 58% of eyes and 0.5 D or lower in 80% of eyes. The TCRP-based calculation resulted in a statistically significantly lower vector error (P<0.01 and significantly more eyes with a vector error ≤0.5 D relative to the VERION-based calculation (P=0.02. The TCRP and VERION keratometry readings suggested a different IOL toric power in 53/83 eyes. In these 53 eyes the TCRP vector error was lower in 28 cases, the VERION error was lower in five cases, and the error was equal in 20 cases. When the anterior cornea had with-the-rule astigmatism, the VERION was more likely to suggest a higher toric power and when the anterior cornea had against-the-rule astigmatism, the VERION was less likely to suggest a higher toric power.Conclusion: Using the TCRP keratometry measurement in the AcrySof toric calculator may improve overall postoperative refractive results
Faruk Kaya; Ibrahim Koçak; Ali Aydin; Hakan Baybora; Koray Karadayi
2016-01-01
AIM:To compare the intraocular lens(IOL)power calculations and refractive outcomes obtained with a new optical biometer and standard ultrasonic biometer in phacoemulsification surgery.METHODS:Thirty-seven eyes of 37 cataract patients who underwent phacoemulsification with IOL implantation were included in this prospective comparative study. The same operator performed biometer measurements in eyes with cataract using a new optical biometer(Aladdin)and a standard ultrasonic biometer(Sonomed AB...
Savini, Giacomo; Hoffer, Kenneth J.; Barboni, Piero; Balducci, Nicole; Schiano-Lomoriello, Domenico; Ducoli, Pietro
2017-01-01
Purpose To investigate the accuracy of a new optical biometer for intraocular lens (IOL) power calculation in eyes undergoing cataract surgery. Methods Consecutive eyes of patients undergoing cataract surgery with the same IOL model were enrolled in a prospective cohort study. Axial length (AL) and corneal power were measured with an optical biometer based on optical low-coherence interferometry and Placido-disc corneal topography. IOL power was calculated with the Hoffer Q, Holladay 1 and SRK/T formulas. For each formula the lens constant was optimized in retrospect in order to achieve a mean prediction error (PE) of zero (difference between the predicted and the postoperative refraction). Median absolute error (MedAE) and percentage of eyes with PE ±0.50 D were calculated. Results Seventy-four eyes of 74 cataract patients were enrolled. The MedAE was 0.25 D with all formulas. A PE within ±0.50 D was obtained in 89.04% of cases with the Hoffer Q and SRK/T formulas, and in 87.67% of cases with the Holladay 1 formula. Conclusions The optical biometer investigated in the present study provides accurate measurements for IOL power calculation. PMID:28231267
Hany A Helaly
2016-01-01
Conclusion: Scheimflug tomography imaging using the Holladay EKR 4 mm improved the accuracy of IOL power calculation in post.LASIK eyes. The best option is a combination of formulas. We recommended the use the combined “Shammas-PL ± Double-K SRK/T formula using EKR 4 mm”h for optical outcomes.
Symbolic algebra approach to the calculation of intraocular lens power following cataract surgery
Hjelmstad, David P.; Sayegh, Samir I.
2013-03-01
We present a symbolic approach based on matrix methods that allows for the analysis and computation of intraocular lens power following cataract surgery. We extend the basic matrix approach corresponding to paraxial optics to include astigmatism and other aberrations. The symbolic approach allows for a refined analysis of the potential sources of errors ("refractive surprises"). We demonstrate the computation of lens powers including toric lenses that correct for both defocus (myopia, hyperopia) and astigmatism. A specific implementation in Mathematica allows an elegant and powerful method for the design and analysis of these intraocular lenses.
Accuracy of Intraocular Lens Power Calculation Formulas for Highly Myopic Eyes
Zhang, Yichi; Liang, Xiao Ying; Liu, Shu; Lee, Jacky W. Y.; Bhaskar, Srinivasan; Lam, Dennis S. C.
2016-01-01
Purpose. To evaluate and compare the accuracy of different intraocular lens (IOL) power calculation formulas for eyes with an axial length (AL) greater than 26.00 mm. Methods. This study reviewed 407 eyes of 219 patients with AL longer than 26.0 mm. The refractive prediction errors of IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) using User Group for Laser Interference Biometry (ULIB) constants were evaluated and compared. Results. One hundred seventy-one eyes were enrolled. The Barrett Universal II formula had the lowest mean absolute error (MAE) and SRK/T and Haigis had similar MAE, and the statistical highest MAE were seen with the Holladay and Hoffer Q formulas. The interquartile range of the Barrett Universal II formula was also the lowest among all the formulas. The Barrett Universal II formulas yielded the highest percentage of eyes within ±1.0 D and ±0.5 D of the target refraction in this study (97.24% and 79.56%, resp.). Conclusions. Barrett Universal II formula produced the lowest predictive error and the least variable predictive error compared with the SRK/T, Haigis, Holladay, and Hoffer Q formulas. For high myopic eyes, the Barrett Universal II formula may be a more suitable choice. PMID:27119018
Accuracy of Intraocular Lens Power Calculation Formulas for Highly Myopic Eyes
Yichi Zhang
2016-01-01
Full Text Available Purpose. To evaluate and compare the accuracy of different intraocular lens (IOL power calculation formulas for eyes with an axial length (AL greater than 26.00 mm. Methods. This study reviewed 407 eyes of 219 patients with AL longer than 26.0 mm. The refractive prediction errors of IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II using User Group for Laser Interference Biometry (ULIB constants were evaluated and compared. Results. One hundred seventy-one eyes were enrolled. The Barrett Universal II formula had the lowest mean absolute error (MAE and SRK/T and Haigis had similar MAE, and the statistical highest MAE were seen with the Holladay and Hoffer Q formulas. The interquartile range of the Barrett Universal II formula was also the lowest among all the formulas. The Barrett Universal II formulas yielded the highest percentage of eyes within ±1.0 D and ±0.5 D of the target refraction in this study (97.24% and 79.56%, resp.. Conclusions. Barrett Universal II formula produced the lowest predictive error and the least variable predictive error compared with the SRK/T, Haigis, Holladay, and Hoffer Q formulas. For high myopic eyes, the Barrett Universal II formula may be a more suitable choice.
Faruk Kaya
2016-05-01
Full Text Available AIM:To compare the intraocular lens(IOLpower calculations and refractive outcomes obtained with a new optical biometer and standard ultrasonic biometer in phacoemulsification surgery.METHODS:Thirty-seven eyes of 37 cataract patients who underwent phacoemulsification with IOL implantation were included in this prospective comparative study. The same operator performed biometer measurements in eyes with cataract using a new optical biometer(Aladdinand a standard ultrasonic biometer(Sonomed AB 5500. Biometric parameters; axial length(AL, keratometric(Kreadings, anterior chamber depth(ACDand IOL power obtained by two devices were recorded. Postoperative actual refractive errors and errors predicted by two devices according to SRK/T formula were analyzed. The mean estimation error(EE, mean absolute estimation error(AEEand the biometric parameters obtained by two biometers were compared.RESULTS:The AL measured by Aladdin(23.45±0.73 mmwas significantly longer than AL by ultrasonic biometer(23.2±0.75 mm(P=0.01. The mean EE and AEE values obtained by Aladdin were significantly smaller than the values by ultrasonic biometer(P=0.0006 and 0.03 respectively. The higher percentage of eyes within ±0.5 and ±1.00 D of target refraction was also found by using Aladdin(67% and 97%.CONCLUSION:The Aladdin optical biometer showed better accuracy and yielded better refractive outcomes compared with ultrasonic biometer.
Ashish Mitra
2014-01-01
Full Text Available Efficacy of intraocular lens power calculation formulas in a subset of Indian myopic population. Retrospectively reviewed 43 patients who underwent phacoemulsification with high axial length (AL (>24.5 mm, range 24.75-32.35 mm. The power of the implanted intraocular lens (IOL was used to calculate the predicted post-operative refractive error by four formulas: Sanders-Retzlaff-Kraff (SRK II, SRK/T, Holladay 1, and Hoffer Q. The predictive accuracy of the formulas was analyzed by comparing the difference between the "actual" and "predicted" postoperative refractive errors. Repeated measures analysis of variance (ANOVA tests were done to have pair-wise comparisons between the formulas and P < 0.05 was considered significant. A subcategory of axial length 24.5-26.5 mm was also tested. Holladay 1, Hoffer Q and SRK/T formulas showed a slight tendency toward resultant hyperopia, with mean error of +0.24 diopters (D, +0.58 D, and +0.92 D, respectively. The Holladay 1 formula provided the best predictive result overall.
Khambhiphant B
2016-07-01
Full Text Available Bharkbhum Khambhiphant,1 Suganlaya Sasiwilasagorn,2 Nattida Chatbunchachai,3 Krit Pongpirul2,4 1Department of Ophthalmology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, 2Department of Ophthalmology, Faculty of Medicine, Chulalongkorn University, Bangkok, 3Department of Ophthalmology, Samut Prakan Hospital, Samut Prakan, Thailand; 4Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA Purpose: The purpose of this study was to evaluate the effect of pupillary dilation on the Haigis formula-calculated intraocular lens (IOL power and ocular biometry measurements by using IOLMaster®. Methods: A prospective study was performed for biometry measurements of 373 eyes of 192 healthy subjects using the IOLMaster at the outpatient department of King Chulalongkorn Memorial Hospital from February 2013 to July 2013. The axial length (AL, anterior chamber depth (ACD, keratometry (K, and IOL power were measured before and after 1% tropicamide eye drop instillation. The Haigis formula was used in the IOL power calculation with the predicted target to emmetropia. Each parameter was compared by a paired t-test prior to and after pupillary dilation. Bland–Altman plots were also used to determine the agreement between each parameter. Results: The mean age of the subjects was 53.74±14.41 years (range 18–93 years. No differences in AL (P=0.03, steepest K (P=0.42, and flattest K (P=0.41 were obtained from the IOLMaster after pupillary dilation. However, ACD and IOL power were significantly different postdilation (P<0.01 and P<0.01, respectively. In ACD and IOL power measurements, the concordance rates were 93.03% and 97.05% within 95% limits of agreement (-0.48 to 0.26 mm and -1.09 to 0.88 D, respectively in the Bland–Altman plots. Conclusion: Biometry measurements in the cycloplegic stage should be considered in the IOL formulas that use parameters other than AL and K. Keywords: Haigis
Khambhiphant, Bharkbhum; Sasiwilasagorn, Suganlaya; Chatbunchachai, Nattida; Pongpirul, Krit
2016-01-01
Purpose The purpose of this study was to evaluate the effect of pupillary dilation on the Haigis formula-calculated intraocular lens (IOL) power and ocular biometry measurements by using IOLMaster®. Methods A prospective study was performed for biometry measurements of 373 eyes of 192 healthy subjects using the IOLMaster at the outpatient department of King Chulalongkorn Memorial Hospital from February 2013 to July 2013. The axial length (AL), anterior chamber depth (ACD), keratometry (K), and IOL power were measured before and after 1% tropicamide eye drop instillation. The Haigis formula was used in the IOL power calculation with the predicted target to emmetropia. Each parameter was compared by a paired t-test prior to and after pupillary dilation. Bland–Altman plots were also used to determine the agreement between each parameter. Results The mean age of the subjects was 53.74±14.41 years (range 18–93 years). No differences in AL (P=0.03), steepest K (P=0.42), and flattest K (P=0.41) were obtained from the IOLMaster after pupillary dilation. However, ACD and IOL power were significantly different postdilation (P<0.01 and P<0.01, respectively). In ACD and IOL power measurements, the concordance rates were 93.03% and 97.05% within 95% limits of agreement (−0.48 to 0.26 mm and −1.09 to 0.88 D, respectively) in the Bland–Altman plots. Conclusion Biometry measurements in the cycloplegic stage should be considered in the IOL formulas that use parameters other than AL and K. PMID:27555746
Huang, David; Tang, Maolong; Wang, Li; Zhang, Xinbo; Armour, Rebecca L.; Gattey, Devin M.; Lombardi, Lorinna H.; Koch, Douglas D.
2013-01-01
Purpose: To use optical coherence tomography (OCT) to measure corneal power and improve the selection of intraocular lens (IOL) power in cataract surgeries after laser vision correction. Methods: Patients with previous myopic laser vision corrections were enrolled in this prospective study from two eye centers. Corneal thickness and power were measured by Fourier-domain OCT. Axial length, anterior chamber depth, and automated keratometry were measured by a partial coherence interferometer. An OCT-based IOL formula was developed. The mean absolute error of the OCT-based formula in predicting postoperative refraction was compared to two regression-based IOL formulae for eyes with previous laser vision correction. Results: Forty-six eyes of 46 patients all had uncomplicated cataract surgery with monofocal IOL implantation. The mean arithmetic prediction error of postoperative refraction was 0.05 ± 0.65 diopter (D) for the OCT formula, 0.14 ± 0.83 D for the Haigis-L formula, and 0.24 ± 0.82 D for the no-history Shammas-PL formula. The mean absolute error was 0.50 D for OCT compared to a mean absolute error of 0.67 D for Haigis-L and 0.67 D for Shammas-PL. The adjusted mean absolute error (average prediction error removed) was 0.49 D for OCT, 0.65 D for Haigis-L (P=.031), and 0.62 D for Shammas-PL (P=.044). For OCT, 61% of the eyes were within 0.5 D of prediction error, whereas 46% were within 0.5 D for both Haigis-L and Shammas-PL (P=.034). Conclusions: The predictive accuracy of OCT-based IOL power calculation was better than Haigis-L and Shammas-PL formulas in eyes after laser vision correction. PMID:24167323
Development of a universal toric intraocular lens calculator
Hjelmstad, David; Sayegh, Samir I.
2014-02-01
We present a method for calculating the ideal toric lens to implant in astigmatic patients following cataract surgery. We show that the online calculators provided by major toric IOL manufacturers are insufficient for both theoretical and practical reasons. We reveal important theoretical shortcomings in their approach, illustrated by a number of cases which demonstrate how the approach can lead to errors in lens selection. Our approach combines the spherical and cylindrical power calculations into one, and allows for lens data from any manufacturer to be used, eliminating the reliance on multiple programs.
Solar powered desalination system using Fresnel lens
Sales, M. T. B. F.
2016-11-01
The Philippines is surrounded by coastal areas and these areas can be a potential source for potable water. This study aims to design and construct a solar powered desalination system using Fresnel lens. The experimental study was conducted using polluted salt water for the sample and desalination was carried out using the designed system. The desalination system was composed of the solar concentrator, solar still and the condenser system. The Fresnel lens was made of acrylic plastic and was an effective solar concentrator. Solar stills made of dark colored glass bottles were effective in absorbing the solar energy. The condenser system made of polybutylene and polystyrene were effective in condensing the vapor at ambient temperature. The shortest time of vaporization of the salt water was at 293 sec and the optimum angle of position of the lens was 36.42°. The amount of condensate collected was directly proportional to the amount of salt water in the solar still. The highest mean efficiency of the designed set-up was 34.82%. The water produced by the solar powered desalination system using Fresnel lens passed the standards set by WHO (World Health Organization) for drinking water.
徐柏升; 顾扬顺
2013-01-01
As the increasing popularity of corneal refractive surgery and the aging of the society population,it presents a major challenge in accurate calculation of intraocular lens (IOL) power in cataract patients with prior refractive surgery.To cope with this situation,great efforts have been made to reveal the sources of calculation error and available corrective process.Essentially,the instrument error,the keratometer index error and the IOL formula error are considered to be the main three sources,whereas other biometric measurements (e.g.axial length) contribute slightly.Numerous established algorithms aim to reduce I0L prediction error mainly through postoperative corneal power correction or direct adjustment of calculated IOL power.However,it presents a confusing of the variety of procedures and formulas for the controversy of optimal choice still going on,so it is important to make comprehensive consideration of reliable historic material,physician's experience,and patient' s expectation when faced with this issues clinically.%如何准确计算角膜屈光手术后白内障患者的人工晶状体(intraocular lens,IOL)度数是常见的临床问题.常规的IOL计算误差主要来源于仪器检测误差、屈光指数误差和公式计算误差,解决方法主要是通过矫正屈光术后角膜屈光度,或直接矫正IOL计算值来减小预测误差.各种方法的临床应用准确性仍存在一些争议,临床医生应根据自己掌握的资料、临床经验和患者的期望选择合适的计算方法.
Wang, Guang-Ji
2007-07-01
A slide rule has been designed to calculate the ocular accommodation of an ametrope corrected with a spectacle lens. The slide rule makes the calculation itself easier to perform than with traditional methods and is easily applicable in a clinical setting. In the slide rule, there are 3 scales indicating the power of the spectacle lens, the viewing distance, and the ocular accommodation. The most accurate accommodative unit was used to design the slide rule. The ocular accommodation is the product of the accommodative unit and the dioptric viewing distance. The calculating results are accurate from +21 diopters to all minus powers of the spectacle lens. In a clinical setting, the patients can be advised how much accommodation they exert before and after the refractive surgeries.
Juan Raúl Hernández Silva
2010-01-01
Full Text Available OBJETIVO: Determinar la efectividad de la fórmula de Haigis en el cálculo del poder dióptrico del lente intraocular. MÉTODOS: Se realizó un estudio descriptivo prospectivo, de pacientes operados de catarata mediante la técnica de Facoemulsificación en el Servicio de Microcirugía del Instituto Cubano de Oftalmología «Ramón Pando Ferrer» entre enero 2007 a enero 2008. Para el cálculo del poder del lente intraocular se empleó el IOL Máster y la fórmula de Haigis. La muestra de 101 pacientes, se seleccionó por el método aleatorio simple, de los cuales 28 fueron intervenidos en ambos ojos, para un total de 129 ojos. RESULTADOS: El equivalente esférico preoperatorio y posoperatorio no tuvieron diferencias, sí existieron entre esfera esperada y la obtenida. La mayor diferencia entre la esfera esperada y la obtenida fue encontrada en los pacientes hipermétropes. El astigmatismo refractivo fue bajo. La longitud axil posoperatoria no se modificó y la mejor agudeza visual sin corrección y con corrección mejoró en más de cuatro líneas en la cartilla de Snellen CONCLUSIÓN: Se demostró la efectividad de la fórmula de Haigis en el cálculo del poder del lente intraocular.OBJECTIVE: To determine the effectiveness of Haigis´formula in the intraocular lens power calculation. METHODS: A prospective and descriptive study was conducted in patients operated from cataract with phacoemulsification technique at the Microsurgery Service of "Ramón Pando Ferrer" Cuban Institute of Opththalmology from January 2007 to January 2008. The IOL Master and the Haigis´formula were used for the intraocular lens power calculation. The sample of 101 patients was selected by the simple random method, of whom 28 underwent surgery in both eyes, for a total number of 129 eyes. RESULTS: The Pre- and the post-operative spherical equivalents did not have any differences; but the expected sphere and the real sphere did show differences. The biggest difference
儿童白内障手术人工晶状体度数计算准确性分析%Accuracy of intraocular lens power calculation in pediatric cataract surgery
赵姝芝; 蔡可丽
2011-01-01
Objective To determine the accuracy of intraocular lens (IOL) power calculation in a group of pseudophakic children. Methods A relrospective analysis of biometric and refractive data was performed on 62 eyes of 37 infants and children, who successfully underwent cataract extraction and IOL implantation. SRKII were used to calculate the IOL power. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 2 months afier surgery by retinoscopy. The data were analyzed to assess the effects of age at the time of surgery, axial length, and primary or secondary intraocular lens implantation on the accuracy of calculation of IOL power. Results For the overall group the mean and median prediction errors were 1.56D (SD 1.43). There were 32 eyes'absolute predictions errors lower than 1D (52%). The mean absolute prediction errors in eyes with axial lengths≤20 mm were 2.75 D (SD 1.66), and in eyes ＞20 mm were 1.06 D (SD 0.93). The mean absolute prediction errors in eyes in children aged≤2 years were 2.38 D (SD 1.65), and in children aged ＞2 years were 1.04D (SD 0.99). The differences between the absolute prediction errors for both axial length and age were statistically significant (P ＜0.01). The mean-absolute prediction errors in eyes with primary IOL implantation were 1.37D (SD 1.35), and secondary intraocular lens implantation were 2.03D (SD 1.56). The differences between the absolute prediction errors primary or secondary intraocular lens implantation, were not statistically significant (P =.22). Conclusions For the overall group IOL power calculation is generally acceptable. In eyes with axial lengths less than 20 mm and in children younger than 2 years of age larger errors can arise, and the variations increase. This study demonstrates the need for an IOL formula specifically designed for pediatric use.%目的 分析儿童眼人工晶状体度数计算的准确性.方法 回顾性研究37例(62只眼)行先天性白内
Effect of infusion bottle height on lens power after lens refilling with and without a plug
Koopmans, SA; Terwee, T; Haitjema, HJ; Kooijman, AC; Barkhof, J
2003-01-01
Purpose: To evaluate the influence of intraoperative infusion bottle height on the power of refilled pig lenses. Setting: Research Laboratory, Pharmacia Intraocular Lens Manufacturing Plant, Groningen, The Netherlands. Methods: This study comprised 2 groups of pig eyes. In 1 group, the lens was refi
郭海科; 金海鹰; Gerd.U.AUFFARTH; 张洪洋
2010-01-01
目的 对准分子激光角膜屈光手术后人工晶状体屈光力的计算方法进行优化,并开发为计算机软件,评价其准确性与可靠性.方法 对人工晶状体屈光力计算方法进行优化,包括:角膜屈光力的矫正计算;人工晶状体有效位置的计算与双K值法(double-K method)的应用;标准化计算公式的应用.将计算方法编写为计算机应用软件(IOL calculator for post-refractive cases).应用该软件对49例角膜屈光手术后的白内障患者的人工晶状体屈光力进行计算,以白内障手术后实际屈光状态为标准,预测屈光状态与实际屈光状态之间的差异为预测误差,预测误差的绝对值为绝对预测误差.以SPSS 11.0软件分析预测误差与绝对预测误差的平均值与分布.结果 白内障手术后屈光状态为-2.50～0.75 D,平均为(-0.78±o.83)D,3眼(6.1%)为正视,36眼(73.5%)为近视,10眼(20.4%)为远视.预测误差为-1.26～1.96 D,平均(-0.02±0.75)D,接近于正视性屈光状态.绝对预测误差为0～1.96 D,平均(0.62±0.42)D,绝对预测误差≤0.5 D者19眼(38.8%),＞0.5 D且≤1.0 D者22眼(44.9%),＞1.0 D且≤1.5 D者7眼(14.3%),＞1.5 D 且≤2.0 D者1眼(2.0%).结论 通过优化计算方法与开发计算机软件,可以充分简化准分子激光角膜屈光手术后人工晶状体屈光力的计算过程,并提高计算的准确性与可靠性.%Objective To evaluate intraocular lens power calculation after laser refractive surgery using an optimized calculation method and self-designed computer software. Methods Intraocular lens power calculation method was optimized in the following aspects: corrective algorithm for corneal power estimation; algorithm for effective lens position estimation and double-K method for intraocular lens power calculation; and standardized formula for intraocular lens power calculation.The calculation method was programmed into self-designed computer software (IOL calculator for post
黄锦海; 杨欣; 王勤美; 成拾明; 陈洁
2012-01-01
目的 比较新型光学低相干反射仪Lenstar与IOLMaster测量人工晶状体(IOL)度数的一致性和准确性.方法 前瞻性对照研究.同一观测者分别应用光学低相干反射仪Lenstar和IOLMaster V5.4测量98例白内障患者157只眼的眼轴长度(AL),角膜曲率值(Km)和前房深度(ACD),比较两种仪器测量眼前节参数的相关性和差异性,并且比较分别使用4种IOL公式(SRK/T、Holldav I、Hoffer Q和Haigis)计算的IOL度数,目标屈光度设定为正视眼.两组数据间比较采用t检验或Wilcoxon检验,两种仪器测量数据进行IOL度数计算的一致性研究采用Bland-Altman法.结果 Lenstar和IOLMaster测量AL的平均值分别为(23.65±1.17)mm和(23.65±1.16)mm,Km值分别为(44.15±1.58)D和(44.17±1.58)D,差异均无统计学意义(P＞0.05),ACD分别为(3.09 ±0.41)mm 和(3.05 ±0.41)mm,差异有统计学意义(P=0.001).两仪器测量同一参数结果均具有高度相关性(所有r＞0.9,P＜0.001).两种仪器应用4种IOL公式计算结果一致性较好,其中应用SRK/T公式计算差异最小,Haigis公式差异相对较大.结论 应用Lenstar测量眼球生物参数具有准确性、非接触性、操作简便、安全而且患者易于接受的优点,为我们提供了白内障术前准确可靠的数据,在白内障人群中与IOLMaster比较具有较好的一致性.%Objective To evaluate the precision of Intraocular Lens (IOL) power calculation using a new optical low-coherence reflectometry biometer (Lenstar) and compare the results with those obtained with IOLMaster.Methods It was a prospective controlled study.Biometry measurements in 157 eyes of 98 cataract patients were performed by the same examiner with Lenstar and IOLMaster.Axial length (AL),corneal keratometry readings (Km),and anterior chamber depth (ACD) were obtained.Correlation and differences of biometry measurements obtained with two biometers were made.Intraocular Lens power were calculated using 4 formulas and the
Vortexlike Power Flow at the Interfaces of Metamaterial Lens
K. Fang
2012-10-01
Full Text Available The metamaterial lens with DPS/DNS/DPS structure has been realized by using the two-dimensional (2D isotropic transmission line approach. We studied the vortexlike power flow at the interfaces of metamaterial lens and validated by the finite-difference time-domain (FDTD simulator. The computational results showing its different conditions near DPS/DNS and other kinds of interfaces are obtained by CST STUDIO SUITE at different frequencies, and demonstrate the intuitionistic power location at the metamaterial lens interfaces.
Refractive power and biometric properties of the nonhuman primate isolated crystalline lens.
Borja, David; Manns, Fabrice; Ho, Arthur; Ziebarth, Noel M; Acosta, Ana Carolina; Arrieta-Quintera, Esdras; Augusteyn, Robert C; Parel, Jean-Marie
2010-04-01
Purpose. To characterize the age dependence of shape, refractive power, and refractive index of isolated lenses from nonhuman primates. Methods. Measurements were performed on ex vivo lenses from cynomolgus monkeys (cyno: n = 120; age, 2.7-14.3 years), rhesus monkeys (n = 61; age, 0.7-13.3 years), and hamadryas baboons (baboon: n = 16; age, 1.7-27.3 years). Lens thickness, diameter, and surface curvatures were measured with an optical comparator. Lens refractive power was measured with a custom optical system based on the Scheiner principle. The refractive contributions of the gradient, the surfaces, and the equivalent refractive index were calculated with optical ray-tracing software. The age dependence of the optical and biometric parameters was assessed. Results. Over the measured age range isolated lens thickness decreased (baboon: -0.04, cyno: -0.05, and rhesus: -0.06 mm/y) and equatorial diameter increased (logarithmically for the baboon and rhesus, and linearly for cyno: 0.07 mm/y). The isolated lens surfaces flattened and the corresponding refractive power from the surfaces decreased with age (-0.33, -0.48, and -0.68 D/y). The isolated lens equivalent refractive index decreased (only significant for the baboon, -0.001 D/y), and as a result the total isolated lens refractive power decreased with age (baboon: -1.26, cyno: -0.97, and rhesus: -1.76 D/y). Conclusions. The age-dependent trends in the optical and biometric properties, growth, and aging, of nonhuman primate lenses are similar to those of the pre-presbyopic human lens. As the lens ages, the decrease in refractive contributions from the gradient refractive index causes a rapid age-dependent decrease in maximally accommodated lens refractive power.
SIMULATE-4 pin power calculations
Bahadir, T. [Studsvik Scandpower, Inc., 1087 Beacon St., Newton, MA 02459 (United States); Lindahl, S. Oe [Studsvik Scandpower AB, Hantverkargatan 2A, SE-722 12 Vasteraas (Sweden)
2006-07-01
A new pin power reconstruction module has been implemented in Studsvik Scandpower's next generation nodal code, SIMULATE-4. Heterogeneous pin powers are calculated by modulating multi-group pin powers from the sub-mesh solver of SIMULATE-4 with pin form factors from single-assembly CASMO-5 lattice calculations. The multi-group pin power model captures instantaneous spectral effects, and actinide tracking on the assembly sub-mesh describes exposure-induced pin power variations. Model details and verification tests against high order multi-assembly transport methods are presented. The accuracy of the new methods is also demonstrated by comparing SIMULATE-4 calculations with measured critical experiment pin powers. (authors)
叶向或; 张广斌; 王乐; 毛益辉; 李孟琼
2011-01-01
目的 对比研究光学低相干反射生物测量仪( Lenstar LS 900)、光学相干生物测量仪(IOL Master)及A型超声扫描3种方法测量眼轴、前房深度及计算所需IOL屈光度,比较3种方法所测数据之间的差异.方法 应用Lenstar LS 900、IOL Master及A型超声扫描仪分别对50例(80眼)白内障患眼进行眼轴及前房深度测量；利用3种设备分别计算所需IOL屈光度,均选用SRK/T计算公式和SA 60 AT(Alcon)人工晶状体,在确定同一度数的前提下比较目标屈光度的差异.结果 Lenstar LS900、IOL Master及A超测量眼轴长度及前房深度,三者所测的数据之间差异无统计学意义,具有良好的相关性.Lenstar LS 900和IOL Master所获得的术后目标值差异无统计学意义(P＞0.05),而B超所获得的术后目标值与另二者获得的结果差异有统计学意义(P＜0.05).Bland-Altman分析显示,3种设备获得的目标屈光值具有良好的一致性,尤其是Lenstar LS 900和IOL Master之间.结论 在白内障患眼的生物测量中,Lenstar LS 900、IOL Master和A超有良好的一致性.同时,Lenstar LS 900还可以快速、准确的为白内障和屈光医生提供更多眼生物信息.%Objective To evaluate axial length (AL),anterior chamber depth (ACD) ; and intraocular lens (IOL) power calculation using a new optical low-coherence reflectometry biometer( Lenstar LS 900) and compare the results with those obtained with a partial coherence intefferometry optical biometer (IOL Master) and A-type ultrasound scan.Methods Biometry measurements in 80 eyes of 50 subjects scheduled for cataract surgery were done by the same examiner with Lenstar LS 900,IOL Master and A-scan.After determination of AL and ACD,IOL power calculation for an AcryS of SA60 AT (Alcon) was compared between the 3 devices using SRK/T formula.Results For the AL and ACD,there were significant linear correlation between the Lenstar LS 900,IOL Master and A-scan.The mean differences in IOL power
Polizzi, A; Schenone, M; Ciurlo, C; Bertagno, R; Molfino, F; Camoriano, G P; Saccà, S C
1998-01-01
Intraocular lens (IOL) power calculation in 46 pseudophakic eyes (extracapsular cataract extraction with IOL in posterior chamber), utilizing a Javal keratometer, a Sonomed A 2000 echobiometer (probe 10 MHz, velocity=1,548 m/s) and the SRK2 formula, although there was a statistically significant reduction of the axial length, both in normal and hyperopic eyes, demonstrated no statistically significant differences of IOL power, when compared to the power previously calculated in the phakic eye.
IOL Power Calculation after Corneal Refractive Surgery
Maddalena De Bernardo
2014-01-01
Full Text Available Purpose. To describe the different formulas that try to overcome the problem of calculating the intraocular lens (IOL power in patients that underwent corneal refractive surgery (CRS. Methods. A Pubmed literature search review of all published articles, on keyword associated with IOL power calculation and corneal refractive surgery, as well as the reference lists of retrieved articles, was performed. Results. A total of 33 peer reviewed articles dealing with methods that try to overcome the problem of calculating the IOL power in patients that underwent CRS were found. According to the information needed to try to overcome this problem, the methods were divided in two main categories: 18 methods were based on the knowledge of the patient clinical history and 15 methods that do not require such knowledge. The first group was further divided into five subgroups based on the parameters needed to make such calculation. Conclusion. In the light of our findings, to avoid postoperative nasty surprises, we suggest using only those methods that have shown good results in a large number of patients, possibly by averaging the results obtained with these methods.
David P Piñero
2015-01-01
Full Text Available Purpose: To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP. Materials and Methods: Clinical data from 25 eyes of 14 patients (age range, 52-77 years and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (P IOLadj based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (n kadj for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELP adj . P IOLadj was compared to the real IOL power implanted (P IOLReal , calculated with the SRK-T formula and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas. Results: No statistically significant differences were found between P IOLReal and P IOLadj when ELP adj was used (P = 0.10, with a range of agreement between calculations of 1.23 D. In contrast, P IOLReal was significantly higher when compared to P IOLadj without using ELP adj and also compared to the values estimated by the other formulas. Conclusions: Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age.
Imalvet Santiesteban García
2010-06-01
. Predomina ron los resultados refractivos con tendencia a la emetropía teniendo en cuenta el componente esférico obtenido en ambos grupos, los cuales también fueron superiores en el grupo I.OBJECTIVE: to compare the effectiveness of the intraocular lens dioptric power calculation using IOL Master and the conventional applanation biometry. METHODS: A sample of 100 eyes (patients, diagnosed with unilateral or bilateral cataract in the preoperative consultation service, was selected through simple random sampling in the Ocular Microsurgery Center in the period from March to September, 2006. They were divided into two groups based on the method for intraocular lens calculation. The variables were preoperative mean axial length, preoperative keratometric average, expected and obtained spheral component, visual acuity without correction and better corrected visual acuity preoperatively and postoperatively. The statistical analysis of the results was made by variance analysis, Student's t test for paired mean comparisons and Chi square. The confidence level of 95 % was used. RESULTS: Among the main results, it was found that the axial length differences between IOL Master and A-Scan applanation biometry was statistically significant. Visual acuity without correction increased 4 lines and the best corrected visual acuity increased 6 lines in the postoperative period of the group I patients. Ninety percent of the group I patients, whose visual acuity was calculated with IOL Master, reached emetropia in terms of the spheral component. CONCLUSIONS: A significant difference but lower than that found in the international studies among the preoperative axial lengths calculated through ILO Master and applanation biometry were evinced. The differences were higher in the lenghts calculated by IOL Master. There was improvement in the number of lines of Snellen´s chart both in the visual acuity without correction and the better corrected visual acuity in the two groups; being better in
FOCUSING BY A HIGH-POWER, LOW-FRESNEL-NUMBER LENS - THE FLY FACET LENS
STAVENGA, DG; VANHATEREN, JH
1991-01-01
Diffraction by fly facet lenses has been investigated by photographing the diffraction patterns at various distances from a facet lens whose power was estimated to be 2.03 x 10(4) D. We studied three different aperture diameters with Fresnel numbers of the order of unity. A large focal shift was pro
Focusing by a high-power, low-Fresnel-number lens : the fly facet lens
Stavenga, D.G.; Hateren, J.H. van
1991-01-01
Diffraction by fly facet lenses has been investigated by photographing the diffraction patterns at various distances from a facet lens whose power was estimated to be 2.03 x 10(4) D. We studied three different aperture diameters with Fresnel numbers of the order of unity. A large focal shift was pro
Influence of contact lens power profile on peripheral refractive error.
de la Jara, Percy Lazon; Sankaridurg, Padmaja; Ehrmann, Klaus; Holden, Brien A
2014-06-01
To measure the power profile across the optic zone (OZ) of four commercially available soft contact lenses and establish the impact on the peripheral refractive error of the eye. The power profiles of a spherical conventional hydrogel contact lens (etafilcon A, J&J Vistakon, Jacksonville, FL USA) and three spherical silicone hydrogel contact lenses (lotrafilcon A and B, CIBA Vision, Duluth, GA USA; enfilcon A, CooperVision, Pleasanton, CA USA) with a labeled power of -3.00 and -6.00 diopters were measured using a Shack-Hartmann wavefront sensor power mapping device. Central and peripheral refraction across the horizontal meridian (nasal and temporal visual field at 20, 30, and 40 degrees) was measured with an open-field autorefractor (Shin Nippon NVision K5001, Osaka Japan) with and without contact lenses in 26 myopic subjects. The relative peripheral refractive error on the eye was estimated and compared with and without contact lenses and between contact lenses. Differences in the distribution of the power profile across the OZ were apparent between contact lens types and powers. No significant differences (p > 0.05) were found between contact lens types for their effect on on-axis refraction. Significant differences (p < 0.05) were found at all peripheral retinal eccentricities between contact lens types. For a given central power, the four contact lenses exhibited variations in optical power across the OZ of the lens. The distribution of optical power across the OZ has an influence on the peripheral refractive error of the eye.
He, Jiangnan; Lu, Lina; He, Xiangui; Xu, Xian; Du, Xuan; Zhang, Bo; Zhao, Huijuan; Sha, Jida; Zhu, Jianfeng; Zou, Haidong; Xu, Xun
2017-01-01
Purpose To report calculated crystalline lens power and describe the distribution of ocular biometry and its association with refractive error in older Chinese adults. Methods Random clustering sampling was used to identify adults aged 50 years and above in Xuhui and Baoshan districts of Shanghai. Refraction was determined by subjective refraction that achieved the best corrected vision based on monocular measurement. Ocular biometry was measured by IOL Master. The crystalline lens power of right eyes was calculated using modified Bennett-Rabbetts formula. Results We analyzed 6099 normal phakic right eyes. The mean crystalline lens power was 20.34 ± 2.24D (range: 13.40–36.08). Lens power, spherical equivalent, and anterior chamber depth changed linearly with age; however, axial length, corneal power and AL/CR ratio did not vary with age. The overall prevalence of hyperopia, myopia, and high myopia was 48.48% (95% CI: 47.23%–49.74%), 22.82% (95% CI: 21.77%–23.88%), and 4.57% (95% CI: 4.05–5.10), respectively. The prevalence of hyperopia increased linearly with age while lens power decreased with age. In multivariate models, refractive error was strongly correlated with axial length, lens power, corneal power, and anterior chamber depth; refractive error was slightly correlated with best corrected visual acuity, age and sex. Conclusion Lens power, hyperopia, and spherical equivalent changed linearly with age; Moreover, the continuous loss of lens power produced hyperopic shifts in refraction in subjects aged more than 50 years. PMID:28114313
王红星; 李筱荣; 张琰; 刘巨平; 刘冕
2012-01-01
目的 比较A型超声测量下6种现代人工晶状体公式(SKT、HAIGIS、HOFFER-Q、SRK-Ⅱ、HOLLADAY、BKINK-Ⅱ)在短眼轴眼(＜22 mm)的准确性应用.方法 前瞻性研究短眼轴白内障眼超声生物参数,人工晶状体植入术前使用A型超声仪、角膜曲率计测量术眼的眼轴长及角膜屈光度,术后1个月电脑验光与检影验光相结合的方法测量术眼获得最佳矫正远视力时的实际屈光度数,回输超声测量的眼轴、角膜屈光度及实际使用的人工晶状体度数,并分别计算术眼用这6种公式的预期屈光度数,预期屈光度与实际屈光度之差绝对值,即绝对屈光误差值.结果 HAIGIS绝对屈光误差最大( 0.9181 ±0.10691)D(P ＜0.01);其他5种公式比较无统计学意义,但SRK-Ⅱ的绝对屈光误差值最小(0.5088±0.07012)D,但在绝对屈光误差值0～0.5 D范围内,SKT公式所占比例最高(34.37％).结论 在目前短眼轴样本量,除HAIGIS外,其他5种公式比较,SRK-Ⅱ的绝对屈光误差值最小,SKT其次;但在绝对屈光误差0～0.5D范围内,SKT公式所占比例最高(34.37％),可见,SKT公式在短眼轴眼提供最准确的预测屈光度;HAIGIS对术后屈光度影响较大,不适合国人短眼轴眼.%Objective To explore the accuracies of intraocular lens(IOL) power calculations by using 6 formulas ( SKT,HAIGIS,HOFFER-Q,SRK-Ⅱ,HOLLADAY,BKINK-Ⅱ) in Chinese short eyes.Methods Data were prospectively collected by identifying eyes of axial length below 22 mm.The axial lengths and keratometry of the 32 short eyes were measured with ultrasonic scanning before operation,and the actual postoperative refraction was measured with the methods of computer and retinoscopy optometry when patients could gain best corrected visual acuity one month after surgery or later.Inputting the axial lengths,keratometry and IOL powers into ultrasonic scanning,the predicted postoperative refraction was calculated with 6 formulas,and differences of
Yang, Que; Wang, Shanshan; Wang, Kai; Zhang, Chunyu; Zhang, Lu; Meng, Qingyu; Zhu, Qiudong
2015-08-01
For normal eyes without history of any ocular surgery, traditional equations for calculating intraocular lens (IOL) power, such as SRK-T, Holladay, Higis, SRK-II, et al., all were relativley accurate. However, for eyes underwent refractive surgeries, such as LASIK, or eyes diagnosed as keratoconus, these equations may cause significant postoperative refractive error, which may cause poor satisfaction after cataract surgery. Although some methods have been carried out to solve this problem, such as Hagis-L equation[1], or using preoperative data (data before LASIK) to estimate K value[2], no precise equations were available for these eyes. Here, we introduced a novel intraocular lens power estimation method by accurate ray tracing with optical design software ZEMAX. Instead of using traditional regression formula, we adopted the exact measured corneal elevation distribution, central corneal thickness, anterior chamber depth, axial length, and estimated effective lens plane as the input parameters. The calculation of intraocular lens power for a patient with keratoconus and another LASIK postoperative patient met very well with their visual capacity after cataract surgery.
Park, Jong Min; Park, So Yeon; Kim, Jung In; Kim, Jin Ho [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of); Wu, Hong Gyun [Dept. of Radiation Oncology, Seoul National University College of Medicine, Seoul (Korea, Republic of)
2015-10-15
Since those organs are small in volume, dose calculation for those organs seems to be more susceptible to the calculation grid size in the treatment planning system (TPS). Moreover, since they are highly radio-sensitive organs, especially eye lens, they should be considered carefully for radiotherapy. On the other hand, in the treatment of head and neck (H and N) cancer or brain tumor that generally involves radiation exposure to eye lens and optic apparatus, intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) techniques are frequently used because of the proximity of various radio-sensitive normal organs to the target volumes. Since IMRT and VMAT can deliver prescription dose to target volumes while minimizing dose to nearby organs at risk (OARs) by generating steep dose gradients near the target volumes, high dose gradient sometimes occurs near or at the eye lenses and optic apparatus. In this case, the effect of dose calculation resolution on the accuracy of calculated dose to eye lens and optic apparatus might be significant. Therefore, the effect of dose calculation grid size on the accuracy of calculated doses for each eye lens and optic apparatus was investigated in this study. If an inappropriate calculation resolution was applied for dose calculation of eye lens and optic apparatus, considerable errors can be occurred due to the volume averaging effect in high dose gradient region.
Abelman, Herven; Abelman, Shirley
2014-01-01
Unacceptable principal powers in well-centred lenses may require a toric over-refraction which differs in nature from the one where correct powers have misplaced meridians. This paper calculates residual (over) refractions and their natures. The magnitude of the power of the over-refraction serves as a general, reliable, real scalar criterion for acceptance or tolerance of lenses whose surface relative curvatures change or whose meridians are rotated and cause powers to differ. Principal powers and meridians of lenses are analogous to eigenvalues and eigenvectors of symmetric matrices, which facilitates the calculation of powers and their residuals. Geometric paths in symmetric power space link intended refractive correction and these carefully chosen, undue refractive corrections. Principal meridians alone vary along an arc of a circle centred at the origin and corresponding powers vary autonomously along select diameters of that circle in symmetric power space. Depending on the path of the power change, residual lenses different from their prescription in principal powers and meridians are pure cross-cylindrical or spherocylindrical in nature. The location of residual power in symmetric dioptric power space and its optical cross-representation characterize the lens that must be added to the compensation to attain the power in the prescription.
Herven Abelman
2014-01-01
Full Text Available Unacceptable principal powers in well-centred lenses may require a toric over-refraction which differs in nature from the one where correct powers have misplaced meridians. This paper calculates residual (over refractions and their natures. The magnitude of the power of the over-refraction serves as a general, reliable, real scalar criterion for acceptance or tolerance of lenses whose surface relative curvatures change or whose meridians are rotated and cause powers to differ. Principal powers and meridians of lenses are analogous to eigenvalues and eigenvectors of symmetric matrices, which facilitates the calculation of powers and their residuals. Geometric paths in symmetric power space link intended refractive correction and these carefully chosen, undue refractive corrections. Principal meridians alone vary along an arc of a circle centred at the origin and corresponding powers vary autonomously along select diameters of that circle in symmetric power space. Depending on the path of the power change, residual lenses different from their prescription in principal powers and meridians are pure cross-cylindrical or spherocylindrical in nature. The location of residual power in symmetric dioptric power space and its optical cross-representation characterize the lens that must be added to the compensation to attain the power in the prescription.
Ultralightweight Fresnel Lens Solar Concentrators for Space Power
ONeill, M. J.; McDanal, A. J.
2000-01-01
The first phase of this project was completed in March 2000, and included the successful technology demonstration of a new ultralightweight photovoltaic concentrator array at the fully functional panel level. The new array is called the Stretched Lens Aurora (SLA) array, and uses deployable, flexible, thin-film silicone rubber Fresnel lenses to focus sunlight onto high efficiency multijunction solar cells, which are mounted to a composite radiator surface for waste heat dissipation. A prototype panel was delivered to NASA Marshall in March 2000, and comprised four side-by-side lenses focussing sunlight onto four side-by-side photovoltaic receivers. This prototype panel was tested by NASA Glenn prior to delivery to NASA Marshall. The best of the four lens/receiver modules achieved 27.4% efficiency at room temperature in the NASA Glenn solar simulator tests. This performance equates to 375 W/sq.m. areal power and 378 W/kg specific power at the fully functional panel level. We believe this to be the first space solar array of any kind to simulataneously meet the two long-standing NASA goals of 300 W/sq.m. and 300 W/kg at the functional panel level. Key results for the first phase of the program have been documented by ENTECH in a Draft Final Technical Report, which is presently being reviewed by NASA, and which should be published in the near future.
A rapid method for measuring intraocular lens power in vitro with a focimeter.
García-Domene, Mari Carmen; Díez-Ajenjo, María Amparo; Peris-Martínez, Cristina; Navea, Amparo; Artigas, José María
2015-11-01
In this paper we describe a new method for measuring the intraocular lens (IOL) power using a focimeter, a negative ophthalmic lens and a saline solution (0.9% NaCl). To test this we measured the power of 58 different IOLs and we compared them with the power stated by the manufacturer. Despite the limitations, the results show a good correlation.
Power Matters: Foucault's "Pouvoir/Savoir" as a Conceptual Lens in Information Research and Practice
Olsson, Michael; Heizmann, Helena
2015-01-01
Introduction: This paper advocates Foucault's notion of pouvoir/savoir (power/knowledge) as a conceptual lens that information researchers might fruitfully use to develop a richer understanding of the relationship between knowledge and power. Methods: Three of the authors' earlier studies are employed to illustrate the use of this conceptual lens.…
Effects of resonator input power on Kerr lens mode-locked lasers
S Kazempour; A Keshavarz; G Honarasa
2015-07-01
Using the ABCD matrix method, the common stability region between the sagittal and tangential planes of a four-mirror Kerr lens mode-locked (KLM) laser cavity is obtained for different ranges of input power. In addition, the effect of the input power on the Kerr lens sensitivity is investigated. Optimal input power and position for highest Kerr lens sensitivity in the stability region are presented and self-starting regime has been achieved. Results show that the resonator input power has a great influence on designing the KLM lasers which can be used in fabricating an optimal femtosecond laser.
Spectra: Time series power spectrum calculator
Gallardo, Tabaré
2017-01-01
Spectra calculates the power spectrum of a time series equally spaced or not based on the Spectral Correlation Coefficient (Ferraz-Mello 1981, Astron. Journal 86 (4), 619). It is very efficient for detection of low frequencies.
David; P.Piero; Vicente; J.Camps; María; L.Ramón; Verónica; Mateo; Rafael; J.Pérez-Cambrodí
2015-01-01
AIM : To evaluate the prediction error in intraocular lens(IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position(ELP).METHODS: Retrospective study including a total of 25 eyes of 13 patients(age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL(Oculentis Gmb H, Germany). In all cases, an adjusted IOL power(P IOLadj) was calculated based on Gaussian optics using a variable keratometric index value(n kadj) for the estimation of the corneal power(P kadj) and on a new value for ELP(ELP adj) obtained by multiple regression analysis.This P IOLadj was compared with the IOL power implanted(P IOLReal) and the value proposed by three conventional formulas(Haigis, Hoffer Q and Holladay Ⅰ).RESULTS: P IOLReal was not significantly different than P IOLadj and Holladay IOL power(P >0.05). In the Bland and Altman analysis, P IOLadj showed lower mean difference(-0.07 D) and limits of agreement(of 1.47 and-1.61 D)when compared to P IOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELP adj was significantly lower than ELP calculated with other conventional formulas(P <0.01) and was found to be dependent on axial length, anterior chamber depth and P kadj. CONCLUSION: Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing thekeratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors.
A Fully Integrated RF-Powered Contact Lens With a Single Element Display.
Pandey, J; Yu-Te Liao; Lingley, Andrew; Mirjalili, R; Parviz, B; Otis, B
2010-12-01
We present progress toward a wirelessly-powered active contact lens comprised of a transparent polymer substrate, loop antenna, power harvesting IC, and micro-LED. The fully integrated radio power harvesting and power management system was fabricated in a 0.13 μm CMOS process with a total die area of 0.2 mm(2). It utilizes a small on-chip capacitor for energy storage to light up a micro-LED pixel. We have demonstrated wireless power transfer at 10 cm distance using the custom IC and on-lens antenna.
Program Calculates Power Demands Of Electronic Designs
Cox, Brian
1995-01-01
CURRENT computer program calculates power requirements of electronic designs. For given design, CURRENT reads in applicable parts-list file and file containing current required for each part. Program also calculates power required for circuit at supply potentials of 5.5, 5.0, and 4.5 volts. Written by use of AWK utility for Sun4-series computers running SunOS 4.x and IBM PC-series and compatible computers running MS-DOS. Sun version of program (NPO-19590). PC version of program (NPO-19111).
Shukla, R. P.; Perera, G. M.; George, M. C.; Venkateswarlu, P.
1990-01-01
A nondestructive technique for measuring the refractive index of a negative lens using a wedged plate interferometer is described. The method can be also used for measuring the refractive index of convex or zero power lenses. Schematic diagrams are presented for the use of a wedged plate interferometer for measuring the refractive index of a concave lens and of a convex lens.
Felipe Cortizas Ré Martins
2009-08-01
Full Text Available Objetivo: Comparar as medidas ecobiométricas pelos métodos de imersão e de contato. Métodos: A biometria ultrassônica foi realizada em 60 olhos, pelo mesmo examinador e com o mesmo aparelho, usando os métodos de contato e de imersão em cada olho. Resultados: A menor média do comprimento axial (23,16 mm foi obtida através do método de contato, e a maior (23,29 mm sob imersão, usando a mesma sonda ultrassônica. A média do desvio padrão entre as repetidas medidas no mesmo olho foi menor (0,02 com a técnica de imersão, e a maior (0,07 com o método de contato, diferença estatisticamente significante (pPurpose: To compare the ultrasound biometry measurements between immersion and contact techniques. Methods: The biometry was made in 60 eyes by the same examiner, using the contact and immersion techniques in each eye. Results: The lower mean axial length (23,16 mm was found in the contact technique, and the greater (23,29 was found in the immersion technique, using the same probe. The lower mean standard deviation between recurrent measures in the same eye was found in the immersion technique, and the greater in the contact procedure, and was found statistically significant (p<0,001. The Pearson's coefficients demonstrated high correlation between the two techniques, in measuring the axial length and anterior chamber depth. Conclusion: The immersion technique have shown more accuracy and reproducibility, avoiding errors in intraocular lens power calculation, and encountering the visual expectations of the patient.
High-Power Wind Turbine: Performance Calculation
Goldaev Sergey V.
2015-01-01
Full Text Available The paper is devoted to high-power wind turbine performance calculation using Pearson’s chi-squared test the statistical hypothesis on distribution of general totality of air velocities by Weibull-Gnedenko. The distribution parameters are found by numerical solution of transcendental equation with the definition of the gamma function interpolation formula. Values of the operating characteristic of the incomplete gamma function are defined by numerical integration using Weddle’s rule. The comparison of the calculated results using the proposed methodology with those obtained by other authors found significant differences in the values of the sample variance and empirical Pearson. The analysis of the initial and maximum wind speed influence on performance of the high-power wind turbine is done
Hsu M
2011-09-01
Full Text Available David L DeMill1, Majid Moshirfar1, Marcus C Neuffer1, Maylon Hsu1, Shameema Sikder21John A Moran Eye Center, University of Utah, Salt Lake City, UT, USA; 2Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USABackground: To compare the average values of the American Society of Cataract and Refractive Surgery (ASCRS and Ocular MD intraocular lens (IOL calculators to assess their accuracy in predicting IOL power in patients with prior laser-in-situ keratomileusis (LASIK or photorefractive keratectomy.Methods: In this retrospective study, data from 21 eyes with previous LASIK or photorefractive keratectomy for myopia and subsequent cataract surgery was used in an IOL calculator comparison. The predicted IOL powers of the Ocular MD SRK/T, Ocular MD Haigis, and ASCRS averages were compared. The Ocular MD average (composed of an average of Ocular MD SRK/T and Ocular MD Haigis and the all calculator average (composed of an average of Ocular MD SRK/T, Ocular MD Haigis, and ASCRS were also compared. Primary outcome measures were mean arithmetic and absolute IOL prediction error, variance in mean arithmetic IOL prediction error, and the percentage of eyes within ±0.50 and ±1.00 D.Results: The Ocular MD SRK/T and Ocular MD Haigis averages produced mean arithmetic IOL prediction errors of 0.57 and –0.61 diopters (D, respectively, which were significantly larger than errors from the ASCRS, Ocular MD, and all calculator averages (0.11, –0.02, and 0.02 D, respectively, all P < 0.05. There was no statistically significant difference between the methods in absolute IOL prediction error, variance, or the percentage of eyes with outcomes within ±0.50 and ±1.00 D.Conclusion: The ASCRS average was more accurate in predicting IOL power than the Ocular MD SRK/T and Ocular MD Haigis averages alone. Our methods using combinations of these averages which, when compared with the individual averages, showed a trend of decreased mean arithmetic IOL
Demill, David L; Moshirfar, Majid; Neuffer, Marcus C; Hsu, Maylon; Sikder, Shameema
2011-01-01
To compare the average values of the American Society of Cataract and Refractive Surgery (ASCRS) and Ocular MD intraocular lens (IOL) calculators to assess their accuracy in predicting IOL power in patients with prior laser-in-situ keratomileusis (LASIK) or photorefractive keratectomy. In this retrospective study, data from 21 eyes with previous LASIK or photorefractive keratectomy for myopia and subsequent cataract surgery was used in an IOL calculator comparison. The predicted IOL powers of the Ocular MD SRK/T, Ocular MD Haigis, and ASCRS averages were compared. The Ocular MD average (composed of an average of Ocular MD SRK/T and Ocular MD Haigis) and the all calculator average (composed of an average of Ocular MD SRK/T, Ocular MD Haigis, and ASCRS) were also compared. Primary outcome measures were mean arithmetic and absolute IOL prediction error, variance in mean arithmetic IOL prediction error, and the percentage of eyes within ±0.50 and ±1.00 D. The Ocular MD SRK/T and Ocular MD Haigis averages produced mean arithmetic IOL prediction errors of 0.57 and -0.61 diopters (D), respectively, which were significantly larger than errors from the ASCRS, Ocular MD, and all calculator averages (0.11, -0.02, and 0.02 D, respectively, all P < 0.05). There was no statistically significant difference between the methods in absolute IOL prediction error, variance, or the percentage of eyes with outcomes within ±0.50 and ±1.00 D. The ASCRS average was more accurate in predicting IOL power than the Ocular MD SRK/T and Ocular MD Haigis averages alone. Our methods using combinations of these averages which, when compared with the individual averages, showed a trend of decreased mean arithmetic IOL prediction error, mean absolute upper limit of IOL prediction error, and variance, while increasing the percentage of outcomes within ±0.50 D.
The Gravity- Powered Calculator, a Galilean Exhibit
Cerreta, Pietro
2014-04-01
The Gravity-Powered Calculator is an exhibit of the Exploratorium in San Francisco. It is presented by its American creators as an amazing device that extracts the square roots of numbers, using only the force of gravity. But if you analyze his concept construction one can not help but recall the research of Galileo on falling bodies, the inclined plane and the projectile motion; exactly what the American creators did not put into prominence with their exhibit. Considering the equipment only for what it does, in my opinion, is very reductive compared to the historical roots of the Galilean mathematical physics contained therein. Moreover, if accurate deductions are contained in the famous study of S. Drake on the Galilean drawings and, in particular on Folio 167 v, the parabolic paths of the ball leaping from its launch pad after descending a slope really actualize Galileo's experiments. The exhibit therefore may be best known as a `Galilean calculator'.
王乐; 张广斌; 叶向彧; 毛益辉; 何雪洪
2012-01-01
Objective To evaluate axial length (AL),anterior chamber depth (ACD) and intraocular lens (IOL) power calculation using a new optical low-coherence reflectometry biometer (Lenstar LS 900) and compare the results with those obtained with A-scan applanation ultrasound scan.Methods Biometry measurements in 80 eyes of 50 subjects scheduled for cataract surgery by the same examiner with Lenstar LS 900 and A-scan.After determination of axial length (AL),and anterior chamber depth (ACD),IOL power calculation for an AcrySof SA60AT (Alcon) was compared between the 2 devices using SRK/T formulas.Results For the AL and ACD,there were significant linear correlation between the Lenstar LS 900 and A-scan.Bland-Altman plots showed comparable degrees of agreement in IOL power measurements as determined by SRK/T formulas by the 2 devices.Conclusions Lenstar LS 900 measurements has better agreement with A-scan in cataractous eyes.It can provide additional information of interest to any cataract or refractive surgeon,such as corneal thickness,lensthickness and so on.%目的 评估及比较A超、Lenstar LS900光学生物测量白内障患者眼轴长度、前房深度、人工晶状体度数的差异.方法 分析2011年3月行白内障超声乳化摘除及人工晶状体植入术的白内障患者50例(80只眼),分别用接触式A超和Lenstar LS900光学生物测量两种方法测量眼轴长度及前房深度差异.选用SRK/T公式及SA60AT (Alcon)人工晶状体常数计算人工晶状体度数,在确定同一度数的前提下比较目标屈光度的差异.结果 Lenstar LS900及A超测量眼轴长度及前房深度之间差异无统计学意义,具有良好的相关性.Bland-Altman分析显示,两种设备获得的人工晶状体目标屈光值具有良好的一致性.结论 Lenstar LS900及A超对白内障术前生物测量结果准确,可靠,可用于白内障术前检查.同时,Lenstar LS900能测量角膜厚度,前房深度、晶状体厚度,视网膜厚度和瞳孔大
Toward a Wirelessly Powered On-Lens Intraocular Pressure Monitoring System.
Chiou, Jin-Chern; Hsu, Shun-Hsi; Liao, Yu-Te; Huang, Yu-Chieh; Yeh, Guan-Ting; Kuei, Cheng-Kai; Dai, Kai-Shiun
2016-09-01
This paper presents a wireless on-lens intraocular pressure monitoring system, comprising a capacitance-to-digital converter and a wirelessly powered radio-frequency identification (RFID)-compatible communication system, for sensor control and data communication. The capacitive sensor was embedded on a soft contact lens of 200 μm thickness using commercially available biocompatible lens material, to improve compliance and reduce user discomfort. The sensor chip was shown to achieve effective number of bits greater than 10 over a capacitance range up to 50 pF while consuming only 64-μW power. The on-lens capacitive sensor could detect dielectric variation caused by changes in water content from a distance of 2 cm by using incident power from an RFID reader at 20 dBm. The maximum detectable distance was 11 cm with 30-dBm incident RF power. The rise in eye tissue temperature under 30-dBm RF exposure over an interval of 1 s was simulated and found to be less than 0.01°C.
Lens of the eye dose calculation for neuro-interventional procedures and CBCT scans of the head
Xiong, Zhenyu; Vijayan, Sarath; Rana, Vijay; Jain, Amit; Rudin, Stephen; Bednarek, Daniel R.
2016-03-01
The aim of this work is to develop a method to calculate lens dose for fluoroscopically-guided neuro-interventional procedures and for CBCT scans of the head. EGSnrc Monte Carlo software is used to determine the dose to the lens of the eye for the projection geometry and exposure parameters used in these procedures. This information is provided by a digital CAN bus on the Toshiba Infinix C-Arm system which is saved in a log file by the real-time skin-dose tracking system (DTS) we previously developed. The x-ray beam spectra on this machine were simulated using BEAMnrc. These spectra were compared to those determined by SpekCalc and validated through measured percent-depth-dose (PDD) curves and half-value-layer (HVL) measurements. We simulated CBCT procedures in DOSXYZnrc for a CTDI head phantom and compared the surface dose distribution with that measured with Gafchromic film, and also for an SK150 head phantom and compared the lens dose with that measured with an ionization chamber. Both methods demonstrated good agreement. Organ dose calculated for a simulated neuro-interventional-procedure using DOSXYZnrc with the Zubal CT voxel phantom agreed within 10% with that calculated by PCXMC code for most organs. To calculate the lens dose in a neuro-interventional procedure, we developed a library of normalized lens dose values for different projection angles and kVp's. The total lens dose is then calculated by summing the values over all beam projections and can be included on the DTS report at the end of the procedure.
Chiou, Jin-Chern; Hsu, Shun-Hsi; Huang, Yu-Chieh; Yeh, Guan-Ting; Liou, Wei-Ting; Kuei, Cheng-Kai
2017-01-07
This study presented a wireless smart contact lens system that was composed of a reconfigurable capacitive sensor interface circuitry and wirelessly powered radio-frequency identification (RFID) addressable system for sensor control and data communication. In order to improve compliance and reduce user discomfort, a capacitive sensor was embedded on a soft contact lens of 200 μm thickness using commercially available bio-compatible lens material and a standard manufacturing process. The results indicated that the reconfigurable sensor interface achieved sensitivity and baseline tuning up to 120 pF while consuming only 110 μW power. The range and sensitivity tuning of the readout circuitry ensured a reliable operation with respect to sensor fabrication variations and independent calibration of the sensor baseline for individuals. The on-chip voltage scaling allowed the further extension of the detection range and prevented the implementation of large on-chip elements. The on-lens system enabled the detection of capacitive variation caused by pressure changes in the range of 2.25 to 30 mmHg and hydration level variation from a distance of 1 cm using incident power from an RFID reader at 26.5 dBm.
Faruk Kaya; Ibrahil KoÇak; Ali Aydin; Hakan Baybora; Koray Karadayi
2016-01-01
目的：比较超乳手术时应用新型光学生物测量仪和标准超声波测量仪计算人工晶状体的屈光度及屈光结果。 方法：前瞻性研究。研究包含37例37眼白内障患者接受白内障超声乳化联合人工晶状体植入术。同一测量人员分别使用新型光学生物测量仪( Aladdin)与标准超声波测量仪( Sonoled AB 5500)对白内障患者进行检测。通过这两种设备记录生物测定参数，包括眼轴长度、角膜曲率、前房深度及人工晶状体屈光度数。分析术后实际屈光不正与两台设备根据SRK/T公式计算的误差，比较两台设备检查结果的平均估计误差( EE )、平均绝对估计误差( AEE)及生物测定参数。 结果：Aladdin测量仪(23.45±0.73 ll )较超声波测量仪(23.2±0.75 ll)检测出的眼轴显著较长(P=0.01)。Aladdin测量仪的EE与AEE均明显小于超声波测量仪( P=0.0006与0.03)。应用Aladdin测量的大多数眼与目标屈光度相差在±0.5(67%)及±1.00(97%)以内。 结论：Aladdin光学生物测量仪较超声波测量仪更精确，屈光结果更准确。%AlM:To compare the intraocular lens ( lOL ) power calculations and refractive outcomes obtained with a new optical biometer and standard ultrasonic biometer in phacoemulsification surgery. METHODS:Thirty-seven eyes of 37 cataract patients who underwent phacoemulsification with lOL implantation were included in this prospective comparative study. The same operator performed biometer measurements in eyes with cataract using a new optical biometer ( Aladdin) and a standard ultrasonic biometer ( Sonomed AB 5500 ) . Biometric parameters;axial length ( AL ) , keratometric ( K ) readings, anterior chamber depth ( ACD ) and lOL power obtained by two devices were recorded. Postoperative actual refractive errors and errors predicted by two devices according to SRK/T formula were analyzed. The mean estimation error ( EE ) , mean absolute estimation error
Oneill, Mark J.; Mcdanal, A. J.; Spears, Don H.
1989-01-01
The primary project objective was to generate a conceptual design for a nominal 5 kW solar dynamic space power system, which uses a unique, patented, transmittance-optimized, dome-shaped, point-focus Fresnel lens as the optical concentrator. Compared to reflective concentrators, the dome lens allows 200 times larger slope errors for the same image displacement. Additionally, the dome lens allows the energy receiver, the power conversion unit (PCU), and the heat rejection radiator to be independently optimized in configuration and orientation, since none of these elements causes any aperture blockage. Based on optical and thermal trade studies, a 6.6 m diameter lens with a focal length of 7.2 m was selected. This lens should provide 87 percent net optical efficienty at 800X geometric concentration ratio. The large lens is comprised of 24 gores, which compactly stow together during launch, and automatically deploy on orbit. The total mass of the microglass lens panels, the graphite/epoxy support structure, and miscellaneous hardware is about 1.2 kg per square meter of aperture. The key problem for the dome lens approach relates to the selection of a space-durable lens material. For the first time, all-glass Fresnel lens samples were successfully made by a sol-gel casting process.
W. F. Harris
2009-12-01
Full Text Available If an intraocular lens is displaced or if its power is changed what are the consequences for the refractive compensation of the eye? Gaussian optics is used to obtain explicit formulae for the sensitivityof the corneal-plane refractive compensation (also called the refraction, refractive state, etc to change in power and axial displacement of a thin intraocular lens implanted in a simple eye. In particular, for a pseudophakic Gullstrand simplified eye with intraocular lens placed 5 mm behind the cornea the sensitivity to errors in the power of the intraocular lens is about 71 . 0 − 71 for an intraocular lens of power for an intraocular lens of power 20 D, that is, the refractive compensation decreases by about 0.71 dioptres per dioptre increase in the power of the intraocular lens. More generally the sensitivity is approximately ( m 0037 . 0 63 . 0 F − − 0.63 ( 003 . 0 63 . 0 − − (0.0037mF where FI is the power of the intraocular lens. Also for Gullstrand’s simplified eye the sensitivity of refractive compensation to axial displacement of the intraocular lens is approximately linear in FI about (64D FI, in fact. That is, for each dioptre of the power of the intraocular lens the refractive compensation increases by about 0.064 dioptres per millimetre of axial displacement towards the retina.
Power calculation of linear and angular incremental encoders
Prokofev, Aleksandr V.; Timofeev, Aleksandr N.; Mednikov, Sergey V.; Sycheva, Elena A.
2016-04-01
Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and transmit the measured values back to the control unit. The capabilities of these systems are undergoing continual development in terms of their resolution, accuracy and reliability, their measuring ranges, and maximum speeds. This article discusses the method of power calculation of linear and angular incremental photoelectric encoders, to find the optimum parameters for its components, such as light emitters, photo-detectors, linear and angular scales, optical components etc. It analyzes methods and devices that permit high resolutions in the order of 0.001 mm or 0.001°, as well as large measuring lengths of over 100 mm. In linear and angular incremental photoelectric encoders optical beam is usually formulated by a condenser lens passes through the measuring unit changes its value depending on the movement of a scanning head or measuring raster. Past light beam is converting into an electrical signal by the photo-detecter's block for processing in the electrical block. Therefore, for calculating the energy source is a value of the desired value of the optical signal at the input of the photo-detecter's block, which reliably recorded and processed in the electronic unit of linear and angular incremental optoelectronic encoders. Automation technology is constantly expanding its role in improving the efficiency of manufacturing and testing processes in all branches of industry. More than ever before, the mechanical movements of linear slides, rotary tables, robot arms, actuators, etc. are numerically controlled. Linear and angular incremental photoelectric encoders measure mechanical motion and
Gabriela Rodrigues Sampaio
2002-04-01
specific formula for evaluation of the IOL dioptric power, to substitute the affected lens. The IOL dioptric power was correlated with weight and sex and left and right eyes. Although some differences were observed between left and right eyes and males and females, body weight was the most important variable to influence IOL dioptric power in dogs.
Calculation of the transverse kicks generated by the bends of a hollow electron lens
Stancari, Giulio
2014-03-25
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam in high-energy accelerators. They were used in the Fermilab Tevatron collider for abort-gap clearing, beam-beam compensation, and halo scraping. A beam-beam compensation scheme based upon electron lenses is currently being implemented in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. This work is in support of a conceptual design of hollow electron beam scraper for the Large Hadron Collider. It also applies to the implementation of nonlinear integrable optics with electron lenses in the Integrable Optics Test Accelerator at Fermilab. We consider the axial asymmetries of the electron beam caused by the bends that are used to inject electrons into the interaction region and to extract them. A distribution of electron macroparticles is deposited on a discrete grid enclosed in a conducting pipe. The electrostatic potential and electric fields are calculated using numerical Poisson solvers. The kicks experienced by the circulating beam are estimated by integrating the electric fields over straight trajectories. These kicks are also provided in the form of interpolated analytical symplectic maps for numerical tracking simulations, which are needed to estimate the effects of the electron lens imperfections on proton lifetimes, emittance growth, and dynamic aperture. We outline a general procedure to calculate the magnitude of the transverse proton kicks, which can then be generalized, if needed, to include further refinements such as the space-charge evolution of the electron beam, magnetic fields generated by the electron current, and longitudinal proton dynamics.
Numerical Calculation of Overhead Power Lines Dynamics
Gogola Roman
2016-11-01
Full Text Available This paper contains results of transient analysis of airflow around the ACSR power line cross-section in unsymmetric multi-span. The forces applied to the power line are obtained from CFD simulations, where the wind induced vibration is studied. Effect of these forces to the maximal displacement of the power line and the maximal mechanical forces in the points of attachment are studied and evaluated.
Juan R. Hernández Silva
2004-12-01
Full Text Available Este trabajo tiene la finalidad de evaluar los resultados refractivos que se alcanzan con la introducción de las constantes personalizadas en las fórmulas de tercera generación para el cálculo del lente intraocular. Se realizó un estudio descriptivo prospectivo cuyo universo está constituido por los pacientes con catarata senil y se seleccionó una muestra aleatoria de 597 casos. Los pacientes fueron clasificados en 7 grupos según las mediciones preoperatorios del promedio queratométrico y la longitud axial. Para dar salida al objetivo propuesto fueron utilizadas las siguientes variables: longitud axial, promedio queratométrico, componente esférico esperado (sep, componente esférico obtenido (ceo, dioptría de lente intraocular implantado (This paper is aimed at evaluating the refractive results attained with the introduction of personalized constants in the third generation formulas for the intraocular lens calculation. A descriptive and prospective study was conducted among the patients with senile cataract, and a randomized sample of 597 cases was selected. Patients were classified into 7 groups according to the preoperative measurements of the keratometric average and the axial longitude. To obtain the proposed objective, the following variables were used: axial longitude, keratometric average, expected spherical component (sep, obtained spherical component (ceo, dioptry of implanted ocular lens (<16, of 17-19, 20-23, 24-27, 28-30 and refractive results. The statistical analysis of the results was made by a varianze analysis, the T test of comparison of means for matched data and Ji square. A confidence level of 95.5 was used. The utilization of personalized constants in the calculation of intraocular lens increased by more than 20 % the good refractive results. No differences were observed in the diverse groups of patients, the type of formula used and the dioptric power of the lens.The S3652 and S3602 lens models presented a
Ilko K. Ilev; Robert W. Faaland; Do-Hyun Kim; Robert H. James; Don Calogero
2008-01-01
We present a novel confocal laser method (CLM) for precise testing of the dioptric power of both positive and negative intraocular lens (IOL) implants. The CLM principle is based on a simple fiber-optic confocal laser design including a single-mode fiber coupler that serves simultaneously as a point light source used for formation of a collimated Gaussian laser beam, and as a highly sensitive confocal point receiver. The CLM approach provides an accurate, repeatable, objective, and fast method for IOL dioptric power measurement over the range from 0 D to greater than =t=30 D under both dry and in-situ simulated conditions.
Numerical Calculation of the Output Power of a MHD Generator
Adrian CARABINEANU
2014-12-01
Full Text Available Using Lazăr Dragoş’s analytic solution for the electric potential we perform some numerical calculations in order to find the characteristics of a Faraday magnetohydrodymamics (MHD power generator (total power, useful power and Joule dissipation power.
Cheng, H W; Jeng, B M; Chen, C Y; Huang, H Y; Chiou, J C; Luo, C H
2013-01-01
This paper proposed a wireless power harvesting system with micro-electro-mechanical-systems (MEMS) fabrication for noninvasive intraocular pressure (IOP) measurement on soft contact lens substructure. The power harvesting IC consists of a loop antenna, an impedance matching network and a rectifier. The proposed IC has been designed and fabricated by CMOS 0.18 um process that operates at the ISM band of 5.8 GHz. The antenna and the power harvesting IC would be bonded together by using flip chip bonding technologies without extra wire interference. The circuit utilized an impedance transformation circuit to boost the input RF signal that improves the circuit performance. The proposed design achieves an RF-to-DC conversion efficiency of 35% at 5.8 GHz.
High-power 200 fs Kerr-lens mode-locked Yb:YAG thin-disk oscillator.
Pronin, O; Brons, J; Grasse, C; Pervak, V; Boehm, G; Amann, M-C; Kalashnikov, V L; Apolonski, A; Krausz, F
2011-12-15
We demonstrate a power-scalable Kerr-lens mode-locked Yb:YAG thin-disk oscillator. It delivers 200 fs pulses at an average power of 17 W and a repetition rate of 40 MHz. At an increased (180 W) pump power level, the laser produces 270 fs 1.1 μJ pulses at an average power of 45 W (optical-to-optical efficiency of 25%). Semiconductor-saturable-absorber-mirror-assisted Kerr-lens mode locking (KLM) and pure KLM with a hard aperture show similar performance. To our knowledge, these are the shortest pulses achieved from a mode-locked Yb:YAG disk oscillator and this is the first demonstration of a Kerr-lens mode-locked thin-disk laser.
Carinou, E; Ferrari, P; Koukorava, C; Krim, S; Struelens, L
2011-03-01
There are many factors that can influence the extremity and eye lens doses of the medical staff during interventional radiology and cardiology procedures. Numerical simulations can play an important role in evaluating extremity and eye lens doses in correlation with many different parameters. In the present study, the first results of the ORAMED (Optimisation of Radiation protection of MEDical staff) simulation campaign are presented. The parameters investigated for their influence on eye lens, hand, wrist and leg doses are: tube voltage, filtration, beam projection, field size and irradiated part of the patient's body. The tube voltage ranged from 60 to 110 kV(p), filtration from 3 to 6 mm Al and from 0 to 0.9 mm Cu. For all projections, the results showed that doses received by the operator decreased with increasing tube voltage and filtration. The magnitude of the influence of the tube voltage and the filtration on the doses depends on the beam projection and the irradiated part of the patient's body. Finally, the influence of the field size is significant in decreasing the doses.
Garff, Kevin; Jensen, Jason D; Cahoon, Judd; Gupta, Isha; Stagg, Brian; Zaugg, Brian E; Barlow, William R; Olson, Randall J
2015-06-01
To determine the optimum power settings in micropulsed ultrasound (US). John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Experimental study. Pig lenses hardened to be comparable to dense human cataracts were cut into 2.0 mm cubes and removed using micropulsed longitudinal US with previously optimized settings (6 milliseconds on and 6 milliseconds off and using a 0.9 mm 30-degree beveled bent phaco tip). The aspiration was set at 40 mL/min and the vacuum level at 550 mm Hg. Twenty lens cubes were tested with the power set from 10% to 100% in increments of 10%. Primary outcome measures were efficiency time (time to lens removal) and chatter (number of times the lens fragment visibly bounced off the tip). Efficiency time decreased with increasing power. There was a correlation between power and efficiency time (R(2) = 0.41, P = .046), which was more substantial between 30% and 100% power (R(2) = 0.71, P = .004). The mean number of chatter events did not differ significantly between power settings (R(2) = 0.012, P = .1195). There was a 5-fold increase in efficiency between 10% power and 20% power, which likely indicates that there is a minimum power threshold for efficient breakup of the lens. Between 20% and 100% power, there was a linear, strong, and statistically significant improvement in efficiency in these lens fragments. In addition, with micropulsed US there was little chatter or microchatter throughout the power range. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
Corneal Asphericity and IOL Power Calculation in Eyes With Aspherical IOLs.
Savini, Giacomo; Hoffer, Kenneth J; Barboni, Piero; Schiano Lomoriello, Domenico; Ducoli, Pietro
2017-07-01
Given that a previous study found that corneal asphericity influences the refractive outcome of intraocular lens (IOL) power calculation by means of thin-lens formulas in eyes with spherical IOLs, the authors aimed to verify whether such influence can also be observed in eyes with aspherical IOLs. In this retrospective comparative case series, IOL power was calculated with the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas in two groups of eyes undergoing phacoemulsification and implantation of an aspherical IOL (Acrysof SN60WF; Alcon Laboratories, Inc., Fort Worth, TX). For each formula, the refractive prediction error was calculated once the constants had been optimized. Biometric data were obtained by partial coherence interferometry in one group and immersion ultrasound biometry and corneal topography in the other. Corneal asphericity was assessed by two different corneal topographers in the optical biometry group (Magellan; Nidek, Gamagori, Japan) and ultrasound biometry group (Keratron, Optikon 2000 Spa, Rome, Italy). The mean Q-value was -0.12 ± 0.08 in the optical biometry group (n = 51) and -0.22 ± 0.14 in the ultrasound biometry group (n = 79). In both groups, linear regression disclosed a statistically significant correlation between the Q-value and the prediction error (the only exception being the SRK/T formula). More negative Q-values were correlated to a positive prediction error, indicating a myopic outcome for prolate corneas. However, the correlation coefficients were lower than those previously reported for spherical IOLs. Corneal asphericity also influences the refractive outcomes of IOL power calculation by thinlens formulas when aspherical IOLs are implanted, although this influence is exerted to a lesser degree compared to spherical IOLs. [J Refract Surg. 2017;33(7):476-481.]. Copyright 2017, SLACK Incorporated.
Experimental Design and Power Calculation for RNA-seq Experiments.
Wu, Zhijin; Wu, Hao
2016-01-01
Power calculation is a critical component of RNA-seq experimental design. The flexibility of RNA-seq experiment and the wide dynamic range of transcription it measures make it an attractive technology for whole transcriptome analysis. These features, in addition to the high dimensionality of RNA-seq data, bring complexity in experimental design, making an analytical power calculation no longer realistic. In this chapter we review the major factors that influence the statistical power of detecting differential expression, and give examples of power assessment using the R package PROPER.
Gonçalves, Ricardo; Carvalho, Nuno B.; Pinho, Pedro
2017-02-01
In the current contest of wireless systems, the last frontier remains the cut of the power cord. In that sense, the interest over wireless energy transfer technologies in the past years has grown exponentially. However, there are still many challenges to be overcome in order to enable wireless energy transfer full potential. One of the focus in the development of such systems is the design of very-high-gain, highly efficient, antennas that can compensate for the propagation loss of radio signals over the air. In this paper, we explore the design and manufacturing process of dielectric lenses, fabricated using a professional-grade desktop 3D printer. Lens antennas are used in order to increase beam efficiency and therefore maximize the efficiency of a wireless power-transfer system operating at microwave frequencies in the Ku band. Measurements of two fabricated prototypes showcase a large directivity, as predicted with simulations. xml:lang="fr"
Herven Abelman; Shirley Abelman
2014-01-01
Unacceptable principal powers in well-centred lenses may require a toric over-refraction which differs in nature from the one where correct powers have misplaced meridians. This paper calculates residual (over) refractions and their natures. The magnitude of the power of the over-refraction serves as a general, reliable, real scalar criterion for acceptance or tolerance of lenses whose surface relative curvatures change or whose meridians are rotated and cause powers to differ. Principal powe...
Lemon Cells Revisited--The Lemon-Powered Calculator.
Swartling, Daniel J.; Morgan, Charlotte
1998-01-01
Describes a demonstration of the principles of a voltaic cell using lemon cells to power a calculator and other items. A lemon fortified with a penny and a galvanized nail produces a potential of one volt. (PVD)
Tkaczyk, Eric R; Mauring, Koit; Tkaczyk, Alan H
2012-10-01
A ray-tracing approach is used to demonstrate efficient application of the vectorial laws of reflection and refraction to computational optics problems. Both the full width at half-maximum (fwhm) and offset of Gaussian beams resulting from off-center reflection and refraction are calculated for spherical and paraboloidal surfaces of revolution. It is found that the magnification and displacement depend nonlinearly on the miscentering. For these geometries, the limits of accuracy of the lens approximation are examined quantitatively. In contrast to the ray-tracing solution, this paraxial approximation would predict a magnification of a beam's fwhm that is independent of miscentering, and an offset linearly proportional to the miscentering. The focusing property of paraboloidal surfaces of revolution is also derived in setting up the calculation.
Lu Zhang
2013-10-01
Full Text Available AIM: To evaluate the clinical feasibility of using a new optical coherence interferometry(IOL-Master, comparing with traditional ultrasonic biometry and manual keratometry in the accuracy and characteristics for intraocular lens calculation of high myopia.METHODS: The measurement of axial length was performed in 60 eyes(30 eyes for each groupwith senile cataract of high myopia(≥-6.00Dusing IOL-Master and ultrasonic biometry. The measurement of corneal power(Kwas also performed in the patient using IOL-Master and manual keratometry preoperatively. Phacoemulsification and foldable lens implantation were done on the patients. IOL power calculation was carried out according to the SRK/T formula on the basis of the group-related data. Best corrected visual acuity, refraction, contrast sensitivity and wave front aberration root mean square(RMSwere re-tested after 3 months postoperatively.RESULTS: Significant difference between the two methods in axial length measurement which was 29.81±1.53mm by ultrasound and 29.63±1.81mm by IOL-Master(P=0.001. And in corneal power measurement which was 43.22±1.67K by manual keratometry and 44.27±1.39K by IOL-Master(P=0.006. There was a significant difference between the two groups(P=0.001. 63.0% vs 31.2% had a mean absolute refractive error(MAREwithin ±0.50 diopter for the IOL-Master and A-scan groups, respectively(χ2=3.1, Pth order aberration, 4th order spherical aberration and total high order aberration in the IOL-Master group were lower than those in the A-scan group at 6mm pupil diameter 3 months later. CONCLUSION: IOL-Master is a non-contact, accurate, safe and reliable tool for calculating IOL power and it is more accurate on the design of the IOL in the cataract surgery on the high myopia patients.
Elección del poder dióptrico de la lente ocular Election of the dioptric power of the ocular lens
Edith María Ballate Nodales
2001-12-01
Full Text Available Se realiza una revisión bibliográfica acerca de la actualización del cálculo del poder dióptrico de la lente intraocular (LIO, se informa sobre las diferentes generaciones de fórmulas para el cálculo, se evalúan los parámetros y variables que influyen en los errores de cálculo y se ofrecen criterios para la decisión a la hora de elegir el poder dióptrico de la lente. El estudio se realizó en 250 ojos en la Consulta de Biometría del Hospital "Hermanos Ameijeiras".A bibliographic review on the updating of the dioptric power calculation of the intraocular lens (IOL was made.The different generations of formulas used for calculating are reported, the parameters and variables influencing on the calculation erros are evaluated and criteria are offered for making decisions at the time of selecting the dioptric power of the lens. The study was conducted in 250 eyes at the Biometry Departrment of "Hermanos Ameijeiras" Hospital.
Behrens, R
2013-07-01
In this work, conversion coefficients from electron fluence to absorbed dose to the eye lens were calculated using Monte Carlo simulations based on a detailed stylised eye model and a very simple but whole body phantom. These data supersede and complement data published earlier based on the simulation of only a single stylised eye. The new data differ from the old ones by not more than 3, 4, 7 and 16 % for angles of radiation incidence of α=0°, 15°, 30° and 45°, respectively, due to the inclusion of the whole body phantom. The data presented in the present work also complement those of a recent report of the International Commission on Radiological Protection (ICRP) (ICRP Publication 116), where conversion coefficients from electron fluence to absorbed dose to the lens of the eye are shown for solely 0°, 180° and isotropic radiation incidence (but for a much broader range of energies). In this article, values are provided for angles of incidence of 0° up to 180° in steps of 15° and for rotational geometry; no systematic deviation was observed from the values given in ICRP Publication 116 for 0° (based on the application of a bare eye) and 180° (based on the application of a voxel whole body phantom). Data are given for monoenergetic electrons from 0.1 up to 10 MeV and for a broad parallel beam geometry in vacuum.
Software for calculation of electric power systems parameters
Rodriguez, Gustavo; Aromataris, Luis; Donolo, Marcos; Hernandez, Jose; Moitre, Diego [Universidad Nacional de Rio Cuarto, Grupo de Analisis de Sistemas Electricos de Potencia (GASEP), Cordoba (Argentina)
2003-07-01
The calculation of power transmission lines parameters of electric energy has a fundamental importance in the design, construction and simulation of electric power systems. Generally, the results obtained are used in the database for the studies of power flow, short circuit and stability . This paper presents a software with graphical interface which allows the estimation of parameters of power transmission lines of electric energy. By means of a tutorial, the user is oriented step by step about the input of data and other features of the line, passing to the calculation stage when the data are correctly and completely entered. The output of the results is shown on the screen on a Pi circuit and through graphics that simulate the voltage drop for a determined load. (Author)
Calculation of the relativistic Bloch correction to stopping power
Ahlen, S. P.
1982-01-01
Bloch's technique of joining the nonrelativistic Bethe and Bohr stopping-power expressions by taking into account wave-packet effects for close collisions is extended to the relativistic case. It is found that Bloch's nonrelativistic correction term must be modified and that charge asymmetric terms appear. Excellent agreement is observed by comparing the results of these calculations to recent data on the stopping power of relativistic heavy ions.
On power and sample size calculation in ethnic sensitivity studies.
Zhang, Wei; Sethuraman, Venkat
2011-01-01
In ethnic sensitivity studies, it is of interest to know whether the same dose has the same effect over populations in different regions. Glasbrenner and Rosenkranz (2006) proposed a criterion for ethnic sensitivity studies in the context of different dose-exposure models. Their method is liberal in the sense that their sample size will not achieve the target power. We will show that the power function can be easily calculated by numeric integration, and the sample size can be determined by bisection.
Scoping calculations of power sources for nuclear electric propulsion
Difilippo, F.C. [Oak Ridge National Lab., TN (United States)
1994-05-01
This technical memorandum describes models and calculational procedures to fully characterize the nuclear island of power sources for nuclear electric propulsion. Two computer codes were written: one for the gas-cooled NERVA derivative reactor and the other for liquid metal-cooled fuel pin reactors. These codes are going to be interfaced by NASA with the balance of plant in order to making scoping calculations for mission analysis.
Optimal power flow calculation for power system with UPFC considering load rate equalization
Liu, Jiankun; Chen, Jing; Zhang, Qingsong
2017-06-01
Unified power flow controller (UPFC) device can change system electrical quantity (such as voltage, impedance, phase angle, etc.) rapidly and flexibly under the premise of maintain security, stability and reliability of power system, thus can improve the transmission power and transmission line utilization, so as to enhance the power supply capacity of the power grid. Based on a thorough study of the steady-state model of UPFC, taking load rate equalization as objective function, the optimal power flow model is established with UPFC, and simplified interior point method is used to solve it. Finally, optimal power flow of 24 continuous sections actual data is calculated on a typical day of Nanjing network. The results show that the optimal power flow calculation with UPFC can optimize the load rate equalization on the basis of eliminating line overload, improving the voltage level of local power network.
The "Gravity-Powered Calculator," a Galilean Exhibit
Cerreta, Pietro
2014-01-01
The Gravity-Powered Calculator is an exhibit of the Exploratorium in San Francisco. It is presented by its American creators as an amazing device that extracts the square roots of numbers, using only the force of gravity. But if you analyze his concept construction one can not help but recall the research of Galileo on falling bodies, the inclined…
The "Gravity-Powered Calculator," a Galilean Exhibit
Cerreta, Pietro
2014-01-01
The Gravity-Powered Calculator is an exhibit of the Exploratorium in San Francisco. It is presented by its American creators as an amazing device that extracts the square roots of numbers, using only the force of gravity. But if you analyze his concept construction one can not help but recall the research of Galileo on falling bodies, the inclined…
FEATURES OF CALCULATION OF THE NONCONTACT ELECTRIC POWER GENERATORS
Kvitko A. V.
2015-10-01
Full Text Available The article shows that to improve the performance of autonomous systems we need new methods and principles of their design, associated with both the use of renewable sources and the application of new technical solutions of electromechanical generators and static stabilizers and inverters electric power settings. We have disclosed modern requirements for generators of electric power, as well as features of calculating the parameters of contactless electrical power generators: asynchronous generators capacitive excitation and asynchronous generators with permanent magnets. The article presents some analytical expressions for calculating the electrical losses and the efficiency of the generators, specific weight and power. It is shown, that expedient to designing contactless electrical power generators to carry out as part of the autonomous electricity supply systems, as it is sometimes advantageous to understate the main criteria of efficiency of generators, in order to improve, for example, weight and overall dimensions of static converters. The conclusion is made that in order to improve the efficiency of designing contactless electrical power generators in the early stages of designing it is necessary to carry out a preliminary assessment of the main criteria of efficiency of contactless electrical machines. We have also discussed analytical expressions, which might be used for preliminary evaluation of application features for various types of contactless generators in the stand-alone electricity supply systems taking into account the conditions of use
Joyce, Karen E; Hayasaka, Satoru
2012-10-01
Although there are a number of statistical software tools for voxel-based massively univariate analysis of neuroimaging data, such as fMRI (functional MRI), PET (positron emission tomography), and VBM (voxel-based morphometry), very few software tools exist for power and sample size calculation for neuroimaging studies. Unlike typical biomedical studies, outcomes from neuroimaging studies are 3D images of correlated voxels, requiring a correction for massive multiple comparisons. Thus, a specialized power calculation tool is needed for planning neuroimaging studies. To facilitate this process, we developed a software tool specifically designed for neuroimaging data. The software tool, called PowerMap, implements theoretical power calculation algorithms based on non-central random field theory. It can also calculate power for statistical analyses with FDR (false discovery rate) corrections. This GUI (graphical user interface)-based tool enables neuroimaging researchers without advanced knowledge in imaging statistics to calculate power and sample size in the form of 3D images. In this paper, we provide an overview of the statistical framework behind the PowerMap tool. Three worked examples are also provided, a regression analysis, an ANOVA (analysis of variance), and a two-sample T-test, in order to demonstrate the study planning process with PowerMap. We envision that PowerMap will be a great aide for future neuroimaging research.
Power transmission line operating modes calculation with controllable phase shifters
Astashev, M. G.; Novikov, M. A.; Panfilov, D. I.; Rashitov, P. A.; Remizevich, T. V.; Fedorova, M. I.
2016-12-01
The article contains the analysis of the influence of the phase shifter (PS) on the energy processes in the power transmission line in terms of the two-unit model of the electric network. The approach to synthesis of the models regulated by the phase shifter providing for both calculation of the steady operation modes of the electric networks with the phase shifters and research of the electromagnetic processes and designing of the device itself is offered.
Stochastic Boundary, Diffusion, Emittance Growth and Lifetime calculation for the RHIC e-lens
Abreu,N.P.; Fischer, W.; Luo, Y.; Robert-Demolaize, G.
2009-01-20
To compensate the large tune shift and tune spread generated by the head-on beam-beam interactions in polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), a low energy electron beam with proper Gaussian transverse profiles was proposed to collide head-on with the proton beam. In this article, using a modified version of SixTrack [1], we investigate stability of the single particle in the presence of head-on beam-beam compensation. The Lyapunov exponent and action diffusion are calculated and compared between the cases without and with beam-beam compensation for two different working points and various bunch intensities. Using the action diffusion results the emittance growth rate and lifetime of the proton beam is also estimated for the different scenarios.
Power and Sample Size Calculations for Contrast Analysis in ANCOVA.
Shieh, Gwowen
2017-01-01
Analysis of covariance (ANCOVA) is commonly used in behavioral and educational research to reduce the error variance and improve the power of analysis of variance by adjusting the covariate effects. For planning and evaluating randomized ANCOVA designs, a simple sample-size formula has been proposed to account for the variance deflation factor in the comparison of two treatment groups. The objective of this article is to highlight an overlooked and potential problem of the exiting approximation and to provide an alternative and exact solution of power and sample size assessments for testing treatment contrasts. Numerical investigations are conducted to reveal the relative performance of the two procedures as a reliable technique to accommodate the covariate features that make ANCOVA design particularly distinctive. The described approach has important advantages over the current method in general applicability, methodological justification, and overall accuracy. To enhance the practical usefulness, computer algorithms are presented to implement the recommended power calculations and sample-size determinations.
Łukaszewska-Smyk, Agnieszka; Kałuzny, Józef
2010-01-01
The lens platform defines lens structure and lens material. Evolution of lens comprises change in their shape, angulation of haptens and transition of three-piece lens into one-piece lens. The lens fall into two categories: rigid (PMMA) and soft (siliconic, acrylic, colameric). The main lens maaterials are polymers (hydrophilic and hydrophobic). The lens platform has an effect on biocompatibility, bioadhesion, stability of lens in capsule, degree of PCO evolution and sensitiveness to laser damages.
Power flow model/calculation for power systems with multiple FACTS controllers
Radman, Ghadir; Raje, Reshma S. [Center for Energy Systems Research, Tennessee Technological University, P.O. Box 5004, Cookeville, Tennessee-38505 (United States)
2007-10-15
This paper presents a new procedure for steady state power flow calculation of power systems with multiple flexible AC transmission system (FACTS) controllers. The focus of this paper is to show how the conventional power flow calculation method can systematically be modified to include multiple FACTS controllers. Newton-Raphson method of iterative solution is used for power flow equations in polar coordinate. The impacts of FACTS controllers on power flow is accommodated by adding new entries and modifying some existing entries in the linearized Jacobian equation of the same system with no FACTS controllers. Three major FACTS controllers (STATic synchronous COMpensator (STATCOM), static synchronous series compensator (SSSC), and unified power flow controller (UPFC)) are studied in this paper. STATCOM is modeled in voltage control mode. SSSC controls the active power of the link to which it is connected. The UPFC controls the active and the reactive power flow of the link while maintaining a constant voltage at one of the buses. The modeling approach presented in this paper is tested on the 9-bus western system coordinating council (WSCC) power system and implemented using MATLAB software package. The numerical results show the robust convergence of the presented procedure. (author)
Preliminary Development of Thermal Power Calculation Code H-Power for a Supercritical Water Reactor
Fan Zhang
2014-01-01
Full Text Available SCWR (Supercritical Water Reactor is one of the promising Generation IV nuclear systems, which has higher thermal power efficiency than current pressurized water reactor. It is necessary to perform the thermal equilibrium and thermal power calculation for the conceptual design and further monitoring and calibration of the SCWR. One visual software named H-Power was developed to calculate thermal power and its uncertainty of SCWR, in which the advanced IAPWS-IF97 industrial formulation was used to calculate the thermodynamic properties of water and steam. The ISO-5167-4: 2003 standard was incorporated in the code as the basis of orifice plate to compute the flow rate. New heat balance model and uncertainty estimate have also been included in the code. In order to validate H-Power, an assessment was carried out by using data published by US and Qinshan Phase II. The results showed that H-Power was able to estimate the thermal power of SCWR.
Calculation of stopping power ratios for carbon ion dosimetry.
Geithner, Oksana; Andreo, P; Sobolevsky, N; Hartmann, G; Jäkel, O
2006-05-07
Water-to-air stopping power ratio calculations for the ionization chamber dosimetry of clinical carbon ion beams with initial energies from 50 to 450 MeV/u have been performed using the Monte Carlo technique. To simulate the transport of a particle in water the computer code SHIELD-HIT v2 was used, which is a newly developed version where substantial modifications were implemented on its predecessor SHIELD-HIT v1 (Gudowska et al 2004 Phys. Med. Biol. 49 1933-58). The code was completely rewritten replacing formerly used single precision variables with double precision variables. The lowest particle transport specific energy was decreased from 1 MeV/u down to 10 keV/u by modifying the Bethe-Bloch formula, thus widening its range for medical dosimetry applications. In addition, the code includes optionally MSTAR and ICRU-73 stopping power data. The fragmentation model was verified and its parameters were also adjusted. The present code version shows excellent agreement with experimental data. It has been used to compute the physical quantities needed for the calculation of stopping power ratios, s(water,air), of carbon beams. Compared with the recommended constant value given in the IAEA Code of Practice, the differences found in the present investigations varied between 0.5% and 1% at the plateau region, respectively for 400 MeV/u and 50 MeV/u beams, and up to 2.3% in the vicinity of the Bragg peak for 50 MeV/u.
Surface-loss power calculations for the LANSCE DTL
Kurennoy, Surgey S [Los Alamos National Laboratory
2008-01-01
The surface losses in the drift-tube linac (DTL) tanks 3 and 4 of the LANSCE linear accelerator are calculated using 3-D electromagnetic modeling with the CST MicroWave Studio (MWS). The results are used to provide more realistic power estimates for the 201.25MHz RF upgrade design within the LANSCE-R project. We compared 3-D MWS results with those from traditional 2-D Superfish computations for DTL cells and their simplified models and found differences on the level of a few percent. The differences are traced to a 3-D effect consisting in a redistribution of the surface currents on the drift tubes (DT) produced by the DT stem. The dependence of MWS results on the mesh size used in computations is also discussed.
Ximen Ji Ye
2000-01-01
In the present paper, Gaussian optical property in the bi-potential electrostatic and the bell-shaped magnetic combined lens - a new theoretical model first proposed in electron optics - has been thoroughly studied. Meanwhile, based on electron optical canonical aberration theory, analytical formulas of third-order geometrical and first-order chromatic aberration coefficients and their computational results have first been derived for this bi-potential electrostatic and bell-shaped magnetic combined lens. It is to emphasized that this theoretical study can be used to estimate third-order geometric and first-order chromatic aberrations and to provide a theoretical criterion for numerical computation in a rotationally symmetric electromagnetic lens.
A power flow solvability identification and calculation algorithm
Echavarren, F.M.; Lobato, E.; Rouco, L. [School of Engineering of Universidad Pontificia Comillas, C/Alberto Aguilera 23, 28015 Madrid (Spain)
2006-01-15
This paper presents a continuation and optimization based algorithm to detect power flow unsolvability. In addition, the algorithm obtains the power flow solution, if it exists, no matter how ill-conditioned the power system is. The proposed algorithm is based on the parameterization of the distance from the starting point to the real power flow to be solved, using a convergence margin. The performance of the algorithm is illustrated considering an highly loaded scenario of the operation of the Spanish power system. (author)
Noll, Daniel [Goethe Univ., Frankfurt (Germany); Stancari, Giulio [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
2015-11-17
An electron lens is planned for the Fermilab Integrable Optics Test Accelerator as a nonlinear element for integrable dynamics, as an electron cooler, and as an electron trap to study space-charge compensation in rings. We present the main design principles and constraints for nonlinear integrable optics. A magnetic configuration of the solenoids and of the toroidal section is laid out. Singleparticle tracking is used to optimize the electron path. Electron beam dynamics at high intensity is calculated with a particle-in-cell code to estimate current limits, profile distortions, and the effects on the circulating beam. In the conclusions, we summarize the main findings and list directions for further work.
DavidP Piero; VicenteJ Camps; MaraL Ramn; VernicaMateo; Roberto Soto-Negro
2016-01-01
目的：：通过评价非球面人工晶状体( intraocular lens, IOL)屈光度的可预测性,初步开发一种计算屈光度( PIOL )的优化算法。方法：本研究纳入植入非球面 IOL ( LENTIS L-313, Oculentis GmbH)65眼,并分为2组：A组8例12眼,PIOL≥23.0D；B组35例53眼,PIOL<23.0D。术后3mo进行屈光度可预测性评价。参考角膜屈光力估计所致的可变性屈光指数计算出校正的IOL度数( PIOLadj )及屈光结果,根据年龄和解剖学因素得出校正的有效晶状体位置( adjusted effective lens position, ELPadj )。结果：术后A、B两组等效球镜度数分别为-0.75~+0.75 D、-1.38~+0.75D。 A、B两组的PIOLadj和实际晶状体屈光度(PIOLReal)之间无统计学差异(P=0.64、0.82)。 Bland-Altman分析显示A、B两组PIOLadj和PIOLReal之间的一致性区间分别为+1.11~-0.96 D和+1.14~-1.18 D。 Hoffer Q公式和Holladay I公式计算PIOLadj和PIOL之间存在临床和统计学上的显著差异(P<0.01)。结论：植入非球面IOL白内障手术的屈光可预测性可通过平行轴光学联合线性法则使角膜屈光力及晶状体位置相关误差最小化。%•AIM: To evaluate the refractive predictability achieved with an aspheric intraocular lens ( IOL ) and to develop a preliminary optimized algorithm for the calculation of its power ( PIOL ) .•METHODS:This study included 65 eyes implanted with the aspheric IOL LENTIS L-313 ( Oculentis GmbH ) that were divided into 2 groups:12 eyes (8 patients) with PIOL≥23. 0 D (group A), and 53 eyes (35 patients) with PIOL<23. 0 D ( group B ). The refractive predictability was evaluated at 3mo postoperatively. An adjusted IOL power ( PIOLadj ) was calculated considering a variable refractive index for corneal power estimation, the refractive outcome obtained, and an adjusted effective lens position ( ELPadj ) according to age and anatomical factors.•RESULTS: Postoperative spherical equivalent ranged from -0. 75 to +0. 75 D and from -1
A simple approach to calculate active power of electrosurgical units
André Luiz Regis Monteiro
Full Text Available Abstract Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables – frequency domain vectors – obtained through Discrete Fourier Transform (DFT applied on time-sampled voltage and current vectors. Results Comparative results between simulations and a practical experiment are presented – all being in accordance with the requirements of the applicable industry standards. Conclusion An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.
This paper provides the EPA Combined Heat and Power Partnership's recommended methodology for calculating fuel and carbon dioxide emissions savings from CHP compared to SHP, which serves as the basis for the EPA's CHP emissions calculator.
Inverse Calculation of Power Density for Laser Surface Treatment
Römer, G.R.B.E.; Meijer, J.
2000-01-01
Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be ca
Inverse calculation of power density for laser surface treatment
Römer, Gerardus Richardus, Bernardus, Engelina; Meijer, J.
2000-01-01
Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be
Inverse calculation of power density for laser surface treatment
Römer, Gerardus Richardus, Bernardus, Engelina; Meijer, J.
2000-01-01
Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be ca
Tufan, Mustafa Çağatay; Namdar, Tuba; Gümüş, Hasan
2013-05-01
The stopping power in some biological compounds for electrons and positrons was calculated over the energy range from 100 eV to 1 GeV. Total stopping power was obtained by summing the electronic (collisional) and radiative stopping power of the target materials and then employing the continuous slowing down approximation (CSDA) to calculate the path length of incident particles in the target. An effective charge approximation was used for the calculation of collisional stopping power, and an analytical expression for the radiation length was applied to obtain the radiative stopping power. Calculations of stopping power and CSDA range were based mostly on analytical expressions, to allow for an easy calculation of these parameters. The results were tabulated and compared with available data.
Kim, Min; Kim, Hyoung Eun; Lee, Dong Hyun; Koh, Hyoung Jun; Lee, Sung Chul
2015-01-01
Purpose To evaluate the accuracy of postoperative refractive outcomes of combined phacovitrectomy for epiretinal membrane (ERM) in comparison to cataract surgery alone. Materials and Methods Thirty-nine eyes that underwent combined phacovitrectomy with intraocular lens (IOL) implantation for cataract and ERM (combined surgery group) and 39 eyes that received phacoemulsification for cataract (control group) were analyzed, retrospectively. The predicted preoperative refractive aim was compared with the results of postoperative refraction. Results In the combined surgery group, refractive prediction error by A-scan and IOLMaster were -0.305±0.717 diopters (D) and -0.356±0.639 D, respectively, compared to 0.215±0.541 and 0.077±0.529 in the control group, showing significantly more myopic change compared to the control group (p=0.001 and p=0.002, respectively). Within each group, there was no statistically significant difference in refractive prediction error between A-scan and IOLMaster (all p>0.05). IOL power calculation using adjusted A-scan measurement of axial length based on the macular thickness of the normal contralateral eye still resulted in significant postoperative refractive error (all ppower estimation in eyes with cataract and ERM, sequential surgery for ERM and cataract may need to be considered. PMID:25837189
Zhang, Yonghui; Wei, Tongbo; Xiong, Zhuo; Shang, Liang; Tian, Yingdong; Zhao, Yun; Zhou, Pengyu; Wang, Junxi; Li, Jinmin
2014-07-01
The light-emitting diodes (LEDs) with single, twin, triple, and quadruple photonic crystals (PCs) on p-GaN are fabricated by multiple-exposure nanosphere-lens lithography (MENLL) process utilizing the focusing behavior of polystyrene spheres. Such a technique is easy and economical for use in fabricating compound nano-patterns. The optimized tilted angle is decided to be 26.6° through mathematic calculation to try to avoid the overlay of patterns. The results of scanning electron microscopy and simulations reveal that the pattern produced by MENLL is a combination of multiple ovals. Compared to planar-LED, the light output power of LEDs with single, twin, triple, and quadruple PCs is increased by 14.78%, 36.03%, 53.68%, and 44.85% under a drive current 350 mA, respectively. Furthermore, all PC-structures result in no degradation of the electrical properties. The stimulated results indicate that the highest light extraction efficiency of LED with the clover-shape triple PC is due to the largest scattering effect on propagation of light from GaN into air.
Women and Power in Schools: Kentucky Today through an Historic Lens
Hyndman, June Overton
2009-01-01
Schools are public entities that reflect the inequalities of communities; inequalities in race, gender, and socioeconomic status. Public schools privilege males through power in leadership positions such as the principalship. This privilege is historically ingrained in the public school structure and invisible to stakeholders. This article…
Environment-based pin-power reconstruction method for homogeneous core calculations
Leroyer, H.; Brosselard, C.; Girardi, E. [EDF R and D/SINETICS, 1 av du General de Gaulle, F92141 Claman Cedex (France)
2012-07-01
Core calculation schemes are usually based on a classical two-step approach associated with assembly and core calculations. During the first step, infinite lattice assemblies calculations relying on a fundamental mode approach are used to generate cross-sections libraries for PWRs core calculations. This fundamental mode hypothesis may be questioned when dealing with loading patterns involving several types of assemblies (UOX, MOX), burnable poisons, control rods and burn-up gradients. This paper proposes a calculation method able to take into account the heterogeneous environment of the assemblies when using homogeneous core calculations and an appropriate pin-power reconstruction. This methodology is applied to MOX assemblies, computed within an environment of UOX assemblies. The new environment-based pin-power reconstruction is then used on various clusters of 3x3 assemblies showing burn-up gradients and UOX/MOX interfaces, and compared to reference calculations performed with APOLLO-2. The results show that UOX/MOX interfaces are much better calculated with the environment-based calculation scheme when compared to the usual pin-power reconstruction method. The power peak is always better located and calculated with the environment-based pin-power reconstruction method on every cluster configuration studied. This study shows that taking into account the environment in transport calculations can significantly improve the pin-power reconstruction so far as it is consistent with the core loading pattern. (authors)
Mohammad Miraftab
2014-01-01
Full Text Available Purpose: To compare the accuracy of Sanders-Retzlaff-Kraff II (SRK II and 3 rd and 4 th generation intraocular lens (IOL formulas and to compare the effect of different anterior chamber depths among the IOL formulas in cataract patients with normal axial length (AL; 22.0-24.5 millimeters, mm. Materials and Methods: A retrospective chart review was performed of patients with normal AL who underwent cataract surgery. The SRK II and 3 rd generation IOL formulas (Hoffer Q, SRK T, Holladay 1 were compared to the 4 th generation Haigis formula. For analysis, preoperative anterior chamber depth (ACD was divided into three subgroups: ≤3, 3-3.5, and ≥ 3.5 mm. The mean error (ME and mean absolute error (MAE of each formula was compared for each subgroup against the total. The difference between the ME and MAE of the formulas were compared for each ACD subgroup. P 0.05, all comparisons. Conclusion: The SRK II formula can predict refraction in patients with normal AL and ACD less than 3 mm with less error and is preferred over other formulas. The Haigis formula is the preferred choice in patients with a normal AL and ACD longer than 3.5 mm. The prediction accuracy of Hoffer Q, SRK T, and Holladay 1 is comparable in normal AL.
H Nadgaran; P Elahi
2006-03-01
In this work, the inhomogeneous equation of heat conduction was exactly solved by applying inhomogeneous boundary conditions for laser crystals of aspect ratio=1 (aspect ratio=radius of the laser rod/length of the laser rod). We have shown that the paraxial ray approximation leads the solution to be a function of 2, that is, the approximation is equivalent to a situation in which a homogeneous pump source is used. The solution was then used to derive expressions for the overall phase shift, focal length of the thermal lens and the end effect induced curvature of the end face. The expressions were then applied to Nd:YAG laser medium. The result shows a meaningful correction of the order of 0.001 cm to the focal length of Nd:YAG rod for 3 W source power and beam waist of 100 m.
Piotr Pruski
2013-12-01
Full Text Available The paper presents the results of calculating the eigenvalues (associated with electromechanical phenomena of the state matrix of the Polish Power System model on the basis of analysis of simulated and measured instantaneous power disturbance waveforms of generating units in Łaziska Power Plant. The method for electromechanical eigenvalue calculations used in investigations consists in approximation of the instantaneous power swing waveforms in particular generating units with the use of the waveforms being a superposition of the modal components associated with the searched eigenvalues and their participation factors. The hybrid optimisation algorithm consisting of the genetic and gradient algorithms was used for computations.
Power calculations using exact data simulation: A useful tool for genetic study designs
van der Sluis, S.; Dolan, C.V.; Neale, M.C.; Posthuma, D.
2008-01-01
Statistical power calculations constitute an essential first step in the planning of scientific studies. If sufficient summary statistics are available, power calculations are in principle straightforward and computationally light. In designs, which comprise distinct groups (e.g., MZ & DZ twins), su
Noll, Daniel
2015-01-01
An electron lens is planned for the Fermilab Integrable Optics Test Accelerator as a nonlinear element for integrable dynamics, as an electron cooler, and as an electron trap to study space-charge compensation in rings. We present the main design principles and constraints for nonlinear integrable optics. A magnetic configuration of the solenoids and of the toroidal section is laid out. Single-particle tracking is used to optimize the electron path. Electron beam dynamics at high intensity is calculated with a particle-in-cell code to estimate current limits, profile distortions, and the effects on the circulating beam. In the conclusions, we summarize the main findings and list directions for further work.
Dialog Structure Through the Lens of Gender, Gender Environment, and Power
Prabhakaran, Vinodkumar; Rambow, Owen
2017-01-01
Understanding how the social context of an interaction affects our dialog behavior is of great interest to social scientists who study human behavior, as well as to computer scientists who build automatic methods to infer those social contexts. In this paper, we study the interaction of power, gender, and dialog behavior in organizational interactions. In order to perform this study, we first construct the Gender Identified Enron Corpus of emails, in which we semi-automatically assign the gen...
Large Space Telescopes Using Fresnel Lens for Power Beaming, Astronomy and Sail Missions
Early, J T
2002-10-15
The concept of using Fresnel optics as part of power beaming, astronomy or sail systems has been suggested by several authors. The primary issues for large Fresnel optics are the difficulties in fabricating these structures and deploying them in space and for astronomy missions the extremely narrow frequency range of these optics. In proposals where the telescope is used to transmit narrow frequency laser power, the narrow bandwidth has not been an issue. In applications where the optic is to be used as part of a telescope, only around 10{sup -5} to limited frequency response of a Fresnel optic is addressed by the use of a corrective optic that will broaden the frequency response of the telescope by three or four orders of magnitude. This broadening will dramatically increase the optical power capabilities of the system and will allow some spectroscopy studies over a limited range. Both the fabrication of Fresnel optics as large as five meters and the use of corrector optics for telescopes have been demonstrated at LLNL. For solar and laser sail missions the use of Fresnel amplitude zone plates made of very thin sail material is also discussed.
Advanced programs for ampacity calculations of power cables
Anders, G.J.; Rodolakis, T.
1996-11-01
For several years the Cable Ampacity Program (CAP) has been used by both utility and consulting engineers involved in thermal design of cable installations. CAP is capable of addressing both steady state and transient thermal rating calculations. A study was conducted to further strengthen the analytical capabilities of CAP in order to accommodate recently introduced changes in the International Standards, and to address particular cable installations often encountered in practice. As a result, CAP features the following improvements: (1) representation of cables on riser poles, (2) improved loss computations, (3) representation of multiple cables per phase, and (4) automatic reading of load curve data from ASCII files. A CAP user manual is included. tabs., figs.
Solar TiO2-assisted photocatalytic degradation of IGCC power station effluents using a Fresnel lens.
Monteagudo, J M; Durán, A; Guerra, J; García-Peña, F; Coca, P
2008-03-01
The heterogeneous TiO2 assisted photocatalytic degradation of wastewater from a thermoelectric power station under concentrated solar light irradiation using a Fresnel lens has been studied. The efficiency of photocatalytic degradation was determined from the analysis of cyanide and formate removal. Firstly, the influence of the initial concentration of H2O2 and TiO2 on the degradation kinetics of cyanides and formates was studied based on a factorial experimental design. Experimental kinetic constants were fitted using neural networks. Results showed that the photocatalytic process was effective for cyanides destruction (mainly following a molecular mechanism), whereas most of formates (degraded mainly via a radical path) remained unaffected. Finally, to improve formates degradation, the effect of lowering pH on their degradation rate was evaluated after complete cyanide destruction. The photooxidation efficiency of formates reaches a maximum at pH around 5-6. Above pH 6, formate anion is subjected to electrostatic repulsion with the negative surface of TiO2. At pH<4.5, formate adsorption and photon absorption are reduced due to some catalyst agglomeration.
Calculated power distribution of a thermionic, beryllium oxide reflected, fast-spectrum reactor
Mayo, W.; Lantz, E.
1973-01-01
A procedure is developed and used to calculate the detailed power distribution in the fuel elements next to a beryllium oxide reflector of a fast-spectrum, thermionic reactor. The results of the calculations show that, although the average power density in these outer fuel elements is not far from the core average, the power density at the very edge of the fuel closest to the beryllium oxide is about 1.8 times the core avearge.
Progressive lens design method based on addition power curve transformation%基于加光曲线变换的渐进镜片设计方法
薛登攀; 李湘宁; 李笑
2012-01-01
Starting with the vertex definition of spectacle lens, the principle and structure of the progressive addition lens, the rule and method of meridian designing are introduced. The type of addition power curve in the periphery area is chose, and then, the surface power distribution of the lens is given by the method based on transformation of meridian addition power law under the boundary conditions. To compare with the traditional methods, this one has the advantages not only in the unified power distribution form of the progressive addition lens, but also with more freedom and flexibility choice for the designer. The lens surface sag, power and astigmatism distribution can be obtained according to differential geometry of curving surface. It is proved by an embodiment that the required progressive addition lens can be designed with this method.%从眼镜片用顶焦度的定义出发,探讨了渐进加光镜片的原理和结构,介绍了子午线设计的原则和方法.选择镜片周边的加光曲线形式,通过在边界条件下对子午加光曲线做变换,确定镜片表面的屈光度分布,给出了基于加光曲线变换的设计方法.与传统方法相比,不仅在形式上统一了渐进加光镜片的屈光度分布,而且还为设计者提供了更自由灵活的选择.利用曲面微分几何原理获得镜片表面面型矢高,计算屈光度和像散分布.通过实例设计表明,此方法可以设计出所需渐进特征的加光镜片.
A Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology
2010-01-01
We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine, for a given turbine diameter and wind speed. This is because a low-pressure region, due to a strong vortex formation behind the broad brim, draws more mass flow to the wind turbine inside the diffu...
Power Loss Calculation and Thermal Modelling for a Three Phase Inverter Drive System
Z. Zhou
2005-12-01
Full Text Available Power losses calculation and thermal modelling for a three-phase inverter power system is presented in this paper. Aiming a long real time thermal simulation, an accurate average power losses calculation based on PWM reconstruction technique is proposed. For carrying out the thermal simulation, a compact thermal model for a three-phase inverter power module is built. The thermal interference of adjacent heat sources is analysed using 3D thermal simulation. The proposed model can provide accurate power losses with a large simulation time-step and suitable for a long real time thermal simulation for a three phase inverter drive system for hybrid vehicle applications.
Gao, Ming-zhi; Chen, Min; Jin, Cheng
2013-01-01
Parallel operation of distributed generation is an important topic for microgrids, which can provide a highly reliable electric supply service and good power quality to end customers when the utility is unavailable. However, there is a well-known limitation: the power sharing accuracy between...... distributed generators in a parallel operation. Frequency and voltage droop is a well-established control method for improving power sharing performance. In this method, the active and reactive power calculations are used to adjust the frequency and amplitude of the output voltage. This paper describes...... the digital implementation of a droop method, and analyzes the influence of power calculation on droop method performance. According to the analysis, the performance of droop control in a digital control system is limited by the accuracy and speed of the power calculation method. We propose an improved power...
Reduction of trend errors in power calculation by linear transformation of measured axial lengths.
Norrby, Sverker; Lydahl, Eva; Koranyi, Gabor; Taube, Mikaela
2003-01-01
To find a method to improve the refractive outcome in short eyes and long eyes without sacrificing the outcome in normal eyes. St. Erik's Eye Hospital, Stockholm, Sweden. In a prospective study, 148 patients eligible for cataract surgery were measured with 2 different A-scans (BVI Axis, B.V. International; Sonomed 1500, Sonomed Inc.). Refraction was determined 6 weeks postoperatively. The postoperative refraction was compared with the refraction predicted by the Holladay 1, Hoffer Q, and SRK/T formulas; formula constants were optimized to give a zero mean error. The mean absolute error (MAE) was used as an outcome measure. The BVI Axis measured consistently shorter than Sonomed 1500. The mean axial lengths (ALs) were 23.033 mm and 23.435 mm, respectively. With the BVI Axis, an MAE of 0.44 diopter (D), 0.44 D, and 0.47 D was obtained, with the Holladay 1, Hoffer Q, and SRK/T formulas, respectively, with a trend toward undercorrecting short eyes and overcorrecting long eyes. The MAE with the Sonomed 1500 was 0.38 D, 0.39 D, and 0.40 D, respectively. By adding 0.402 mm to each measured value in the BVI Axis data set, the mean AL was transformed to 23.435 mm. With the transformed data, the MAE improved to 0.42 D, 0.43 D, and 0.44 D, respectively, with a reduced trend toward undercorrection and overcorrection. The 0.04 D difference between the instruments, although not statistically significant, may depend on measurement precision. Extending the concept of transformation, a minimum MAE of 0.41 D was obtained with the Holladay 1 at a mean AL of 24.0 mm, 0.43 D with Hoffer Q at 23.9 mm, and 0.40 D with SRK/T at 24.4 mm. The trend toward undercorrection and overcorrection was eliminated at the optimum for each formula. There were systematic differences in measured AL depending on equipment. Thus, the calculated powers differed and caused error in the degree of compliance between the labeled formula constant of an intraocular lens and the equipment used. Although
Numerical implementation of generalized Coddington equations for ophthalmic lens design
Rojo, P.; Royo, S.; Ramírez, J.; Madariaga, I.
2014-02-01
A method for general implementation in any software platform of the generalized Coddington equations is presented, developed, and validated within a Matlab environment. The ophthalmic lens design strategy is presented thoroughly, and the basic concepts of generalized ray tracing are introduced. The methodology for ray tracing is shown to include two inter-related processes. Firstly, finite ray tracing is used to provide the main direction of propagation of the considered ray at the incidence point of interest. Afterwards, generalized ray tracing provides the principal curvatures of the local wavefront at that point, and its orientation after being refracted by the lens. The curvature values of the local wavefront are interpreted as the sagital and tangential powers of the lens at the point of interest. The proposed approach is validated using a double-check of the calculated lens performance in the spherical lens case: while finite ray tracing is validated using a commercial ray tracing software, generalized ray tracing is validated using a software application for ophthalmic lens design based on the classical version of Coddington equations. Equations of the complete tracing process are developed in detail for the case of generic astigmatic ophthalmic lenses as an example. Three-dimensional representation of the sagital and tangential powers of the ophthalmic lens at all directions of gaze then becomes possible, and results are presented for lenses with different geometries.
Calculation of some power indices of mixers with blades of complex geometrical form
K.K. Miroshnychenko
2012-04-01
Full Text Available The calculation of some power indices of mixers with the use of blades of complex geometrical form, providing the effective mode of interfusion of fibrous concrete compositions, is offered.
Spent Fuel Source Term Calculation of Daya Bay Nuclear Power Plant
XU; Zhi-long; WAN; Hai-xia; LI; Long; WU; Xiao-chun; SHAO; Jing; LIU; Li-li; ZHANG; Jing
2013-01-01
The spent fuel of nuclear power plant should be transported to reprocessing plant for reprocessing after reserving for a period of time.Before that,safety analysis and environmental impact assessment should be carried on to the transportation process,which need radioactive source term calculation and analysis.The task of Daya Bay Nuclear Power Plant spent fuel source term calculation includes estimation of
Water Power Calculator Temperature and Analog Input/Output Module Ambient Temperature Testing
Mark D. McKay
2011-02-01
Water Power Calculator Temperature and Analog input/output Module Ambient Temperature Testing A series of three ambient temperature tests were conducted for the Water Power Calculator development using the INL Calibration Laboratory’s Tenney Environmental Chamber. The ambient temperature test results demonstrate that the Moore Industries Temperature Input Modules, Analog Input Module and Analog Output Module, ambient temperature response meet or exceed the manufactures specifications
Model-Based Radar Power Calculations for Ultra-Wideband (UWB) Synthetic Aperture Radar (SAR)
2013-06-01
performance in complex scenarios. Among these scenarios are ground penetrating radar and forward-looking radar for landmine and improvised explosive...Model-Based Radar Power Calculations for Ultra-Wideband (UWB) Synthetic Aperture Radar (SAR) by Traian Dogaru ARL-TN-0548 June 2013...2013 Model-Based Radar Power Calculations for Ultra-Wideband (UWB) Synthetic Aperture Radar (SAR) Traian Dogaru Sensors and Electron
"Cloud" functions and templates of engineering calculations for nuclear power plants
Ochkov, V. F.; Orlov, K. A.; Ko, Chzho Ko
2014-10-01
The article deals with an important problem of setting up computer-aided design calculations of various circuit configurations and power equipment carried out using the templates and standard computer programs available in the Internet. Information about the developed Internet-based technology for carrying out such calculations using the templates accessible in the Mathcad Prime software package is given. The technology is considered taking as an example the solution of two problems relating to the field of nuclear power engineering.
Tae-Yong Park
2017-01-01
Full Text Available Cube satellites have a limitation for generating power because of their cubic structure and extremely small size. In addition, the incidence angle between the sun and the solar panels continuously varies owing to the revolution and rotation of the satellite according to the attitude control strategy. This angle is an important parameter for determining the power generation performance of the cube satellite. In this study, we performed an experimental feasibility study that uses a Fresnel lens as a solar-energy collection system for cube satellite applications, so that the power generation efficiency can be enhanced under the worst incidence angle condition between the sun and solar panels by concentrating and redirecting solar energy onto the solar panels with a commercial Fresnel lens. To verify the effectiveness of the proposed system, we conducted a power-measurement test using a solar simulator and Fresnel lenses at various angles to the light source. In addition, we predicted the on-orbit power-generation enhancement achieved by employing the solar-energy collection system with various attitude control strategies.
A NEW METHOD TO CALCULATE COMPENSATION CURRENT IN PARALLEL ACTIVE POWER FILTER
Ahmet ALTINTAŞ
2004-03-01
Full Text Available Nowadays, active power filter plays an important role in reducing harmonic current and reactive power in power lines. The reliability and effectiveness of an active power filter depends basically on three characteristics. These are the modulation method, the design characteristics of the PWM modulator and the method implemented to generate compensation current. For the last one, there are many proposed methods. Most of them complicated and hence difficult to implement and adjust. In this study, a new method to calculate compensation current is improved and tested in single-phase parallel active power filter controlled by microcontroller. Experimental and simulation results are presented in the paper.
Shan Yang
2016-01-01
Full Text Available Power flow calculation and short circuit calculation are the basis of theoretical research for distribution network with inverter based distributed generation. The similarity of equivalent model for inverter based distributed generation during normal and fault conditions of distribution network and the differences between power flow and short circuit calculation are analyzed in this paper. Then an integrated power flow and short circuit calculation method for distribution network with inverter based distributed generation is proposed. The proposed method let the inverter based distributed generation be equivalent to Iθ bus, which makes it suitable to calculate the power flow of distribution network with a current limited inverter based distributed generation. And the low voltage ride through capability of inverter based distributed generation can be considered as well in this paper. Finally, some tests of power flow and short circuit current calculation are performed on a 33-bus distribution network. The calculated results from the proposed method in this paper are contrasted with those by the traditional method and the simulation method, whose results have verified the effectiveness of the integrated method suggested in this paper.
A Comparative Study of Power and Sample Size Calculations for Multivariate General Linear Models
Shieh, Gwowen
2003-01-01
Repeated measures and longitudinal studies arise often in social and behavioral science research. During the planning stage of such studies, the calculations of sample size are of particular interest to the investigators and should be an integral part of the research projects. In this article, we consider the power and sample size calculations for…
A New Parallel Algorithm in Power Flow Calculation: Dynamic Asynchronous Parallel Algorithm
无
2000-01-01
Based on the general methods in power flow calculation of power system and onconceptions and classifications of parallel algorithm, a new approach named DynamicAsynchronous Parallel Algorithm that applies to the online analysis and real-time dispatching and controlling of large-scale power network was put forward in this paper. Its performances of high speed and dynamic following have been verified on IEEE-14 bus system.
Fast calculation of the maximum power point of photovoltaic generators under partial shading
Carlos Andres Ramos-Paja; Luz Adriana Trejos-Grisales; Javier Herrera-Murcia
2016-01-01
This paper presents a method to calculate the energy production of photovoltaic generators considering partial shading or mismatched conditions. The proposed method is based on the complete one-diode model including the bypass diode in its exponential form, where the current and voltage values of the modules composing the photovoltaic panel array are calculated without using the Lambert-W function. In addition, the method introduces a procedure to calculate the vicinity of the maximum power p...
Axial power distribution calculation using a neural network in the nuclear reactor core
Kim, Y. H.; Cha, K. H.; Lee, S. H. [Korea Electric Power Research Institute, Taejon (Korea, Republic of)
1997-12-31
This paper is concerned with an algorithm based on neural networks to calculate the axial power distribution using excore detector signals in the nuclear reactor core. The fundamental basis of the algorithm is that the detector response can be fairly accurately estimated using computational codes. In other words, the training set, which represents relationship between detector signals and axial power distributions, for the neural network can be obtained through calculations instead of measurements. Application of the new method to the Yonggwang nuclear power plant unit 3 (YGN-3) shows that it is superior to the current algorithm in place. 7 refs., 4 figs. (Author)
2012-01-01
The integrated power generation system of wind, photovoltaic （PV） and energy storage is composed of several wind turbines, PV units and energy storage units. The detailed model of integrated generation is not suitable for the large-scale powe.r system simulation because of the model＇s complexity and long computation time. An equivalent method for power flow calculation and transient simulation of the integrated generation system is proposed based on actual projects, so as to establish the foundation of such integrated system simulation and analysis.
Calculations on the stopping power of a heterogeneous Warm Dense Matter
Casas, David; Schnürer, Matthias; Barriga-Carrasco, Manuel D; Morales, Roberto; González-Gallego, Luis
2015-01-01
The stopping power of Warm Dense Matter (WDM) is estimated by means of the individual contributions of free electrons and bound electrons existing in this special kind of matter, located between classical and degenerate plasmas. For free electrons, the dielectric formalism, well described in previous works of our research group, is used to estimate free electron stopping power. For bound electrons, mean excitation energy of ions is used. Excitation energies are obtained through atomic calculations of the whole atom or, shell by shell in order to estimate their stopping power. Influence of temperature and density is analyzed in case of an impinging projectile. This influence became important for low projectile velocities and negligible for high ones. Using both analysis, the stopping power of an extended WDM is inferred from a dynamical calculation of energy transferred from the projectile to the plasma, where the Bragg peak and stopping range are calculated. Finally, this theoretical framework is used to stud...
Analytic Models of Plausible Gravitational Lens Potentials
Baltz, Edward A.; Marshall, Phil; Oguri, Masamune
2007-05-04
Gravitational lenses on galaxy scales are plausibly modeled as having ellipsoidal symmetry and a universal dark matter density profile, with a Sersic profile to describe the distribution of baryonic matter. Predicting all lensing effects requires knowledge of the total lens potential: in this work we give analytic forms for that of the above hybrid model. Emphasizing that complex lens potentials can be constructed from simpler components in linear combination, we provide a recipe for attaining elliptical symmetry in either projected mass or lens potential.We also provide analytic formulae for the lens potentials of Sersic profiles for integer and half-integer index. We then present formulae describing the gravitational lensing effects due to smoothly-truncated universal density profiles in cold dark matter model. For our isolated haloes the density profile falls off as radius to the minus fifth or seventh power beyond the tidal radius, functional forms that allow all orders of lens potential derivatives to be calculated analytically, while ensuring a non-divergent total mass. We show how the observables predicted by this profile differ from that of the original infinite-mass NFW profile. Expressions for the gravitational flexion are highlighted. We show how decreasing the tidal radius allows stripped haloes to be modeled, providing a framework for a fuller investigation of dark matter substructure in galaxies and clusters. Finally we remark on the need for finite mass halo profiles when doing cosmological ray-tracing simulations, and the need for readily-calculable higher order derivatives of the lens potential when studying catastrophes in strong lenses.
Method for Calculating CO2 Emissions from the Power Sector at the Provincial Level in China
MA Cui-Mei; GE Quan-Sheng
2014-01-01
Based on the detailed origins of each province’s electricity consumption, a new method for calculating CO2 emissions from the power sector at the provincial level in China is proposed. With this so-called consumer responsibility method, the emissions embodied in imported electricity are calculated with source-specific emission factors. Using the new method, we estimate CO2 emissions in 2005 and 2010. Compared with those derived from the producer responsibility method, the power exporters’ emissions decreased sharply. The emissions from the power sector in Inner Mongolia, the largest power exporter of China, decreased by 109 Mt in 2010. The value is equivalent to those from Shaanxi’s power production and Canada’s power and heat production. In contrast, the importers’ emissions increased substantially. The emissions from the power sector in Hebei, the largest power importer of China, increased by 74 Mt. Emissions of Beijing, increased by 60 Mt (320%), in 2010. Thus, we suggest that the Chinese government should take the emissions, as calculated from the consumption perspective, into account when formulating and assessing local CO2 emission reduction targets.
Estimation of the hybrid lens parameters through rigid gas permeable lens fitting
Hasani, Mohammadali; Hashemi, Hassan; Jafarzadehpur, Ebrahim; Yekta, Abbas Ali; Dadbin, Nooshin; khabazkhoob, Mehdi
2016-01-01
Purpose To estimate the fitting parameters of the hybrid contact lens in patients with corneal ectasia using the rigid gas permeable (RGP) lens. Methods Thirty-four eyes with corneal ectasia were evaluated in this study. The patients were examined once with the RGP lens and once with the hybrid contact lens. The relationship between the base curvature of the RGP and the vault of the hybrid lens and the correlation between their powers were analyzed. Results We found a linear relationship betw...
E. P. Zabello
2005-01-01
Full Text Available The method is proposed to make a correction in payment for consumption of reactive energy and power which is attributed to deviation of actual activation energy losses for reactive power compensation from their standard value. It is recommended to calculate standard loss values for every voltage level and actual loss values are to be determined with the help of application of remote electronic accounting means in the current mode of power consumption.
LASER INDUCED THERMAL LENS EFFECT
沈俊; 黄孟才; 江景云; 施教芳
1991-01-01
The thermal lens effect has emerged in recent years as a novel ,highly sensitive tool for the study of the very weak molecular absorption of light energy,This paper discusses the theory and technique of the thermal lens measurement.Some opplications of the thermal lens measurement are described.A mode-mismatched dual-beam thermal lens experimental arragement with a modulated probe beam ,designed by the authors.for trace analysis is presented,and its detection limit was found to be 4.1×10-7 for Cu(Ⅱ) in ethanol and 80 mW excitation power.
A theoretical model for calculation of molecular stopping power. Ph.D. Thesis
Xu, Y. J.
1984-01-01
A modified local plasma model is established. The Gordon-Kim's molecular charged density model is employed to obtain a formula to evaluate the stopping power of many useful molecular systems. The stopping power of H2 and He gas was calculated for incident proton energy ranging from 100 keV to 2.5 MeV. The stopping power of O2, N2, and water vapor was also calculated for incident proton energy ranging from 40 keV. to 2.5 MeV. Good agreement with experimental data was obtained. A discussion of molecular effects leading to department from Bragg's rule is presented. The equipartition rule and the effect of nuclear momentum recoiling in stopping power are also discussed.
Calculation and Simulation Study on Transient Stability of Power System Based on Matlab/Simulink
Shi Xiu Feng
2016-01-01
Full Text Available The stability of the power system is destroyed, will cause a large number of users power outage, even cause the collapse of the whole system, extremely serious consequences. Based on the analysis in single machine infinite system as an example, when at the f point two phase ground fault occurs, the fault lines on either side of the circuit breaker tripping resection at the same time,respectively by two kinds of calculation and simulation methods of system transient stability analysis, the conclusion are consistent. and the simulation analysis is superior to calculation analysis.
Beloglovsky, A.A.; Burmistrov, M.M.; Orlov, A.V.; Vinokurov, V.N. [Moscow Power Engineering Institute, (Russian Federation)
1997-12-31
The development of a method used for calculating electromagnetic industrial frequencies was presented. The FIELD 3.0 program can be used for calculations of near high voltage overhead power transmission lines and substations. In this study, 500 and 750 kV power transmission lines and 750 kV substation fields were computed and compared with measured data. Good agreement was found between measured and computed results, confirming that the FIELD 3.0 software can be a useful tool for successfully determining the electromagnetic field around complicated objects. 8 refs., 5 figs.
Monte Carlo calculation of the neutron and gamma sensitivities of self-powered detectors
Pytel, K.
1981-01-01
A calculational model is presented for the self-powered detector response prediction in various radiation environments. The fast beta particles and electron transport is treated by Monte Carlo technique. A new model of electronic processes within the insulator is introduced. Calculated neutron and gamma sensitivities of five detectors (with Rh, V, Co, Ag and Pt emitters) are compared with reported experimental values. The comparison gives a satisfactory agreement for the majority of examined detectors.
Naftal', M. M.; Baranenko, V. I.; Gulina, O. M.
2014-06-01
The results obtained from calculations of flow accelerated corrosion of equipment and pipelines operating at nuclear power plants constructed on the basis of PWR, VVER, and RBMK reactors carried out using the EKI-02 and EKI-03 software tools are presented. It is shown that the calculation error does not exceed its value indicated in the qualification certificates for these software tools. It is pointed out that calculations aimed at predicting the service life of pipelines and efficient surveillance of flow accelerated corrosion wear are hardly possible without using the above-mentioned software tools.
Power and Sample Size Calculations for Logistic Regression Tests for Differential Item Functioning
Li, Zhushan
2014-01-01
Logistic regression is a popular method for detecting uniform and nonuniform differential item functioning (DIF) effects. Theoretical formulas for the power and sample size calculations are derived for likelihood ratio tests and Wald tests based on the asymptotic distribution of the maximum likelihood estimators for the logistic regression model.…
V. Rusan
2012-01-01
Full Text Available The paper considers calculation methods for reliability of agricultural distribution power networks while using Boolean algebra functions and analytical method. Reliability of 10 kV overhead line circuits with automatic sectionalization points and automatic standby activation has been investigated in the paper.
Klöckner, Wolf; Lattermann, Clemens; Pursche, Franz; Büchs, Jochen; Werner, Sören; Eibl, Dieter
2014-01-01
Disposable orbitally shaken bioreactors are a promising alternative to stirred or wave agitated systems for mammalian and plant cell cultivation, because they provide a homogeneous and well-defined liquid distribution together with a simple and cost-efficient design. Cultivation conditions in the surface-aerated bioreactors are mainly affected by the size of the volumetric oxygen transfer area (a) and the volumetric power input (P∕VL ) that both result from the liquid distribution during shaking. Since Computational Fluid Dynamics (CFD)-commonly applied to simulate the liquid distribution in such bioreactors-needs high computing power, this technique is poorly suited to investigate the influence of many different operating conditions in various scales. Thus, the aim of this paper is to introduce a new mathematical model for calculating the values of a and P∕VL for liquids with water-like viscosities. The model equations were derived from the balance of centrifugal and gravitational forces exerted during shaking. A good agreement was found among calculated values for a and P∕VL , CFD simulation values and empirical results. The newly proposed model enables a time efficient way to calculate the oxygen transfer areas and power input for various shaking frequencies, filling volumes and shaking and reactor diameters. All these parameters can be calculated fast and with little computing power.
Power and Sample Size Calculations for Logistic Regression Tests for Differential Item Functioning
Li, Zhushan
2014-01-01
Logistic regression is a popular method for detecting uniform and nonuniform differential item functioning (DIF) effects. Theoretical formulas for the power and sample size calculations are derived for likelihood ratio tests and Wald tests based on the asymptotic distribution of the maximum likelihood estimators for the logistic regression model.…
Palukuru NAGENDRA
2010-12-01
Full Text Available In this study, the use of artificial neural network (ANN based model, multi-layer perceptron (MLP network, to compute the transfer capabilities in a multi-area power system was explored. The input for the ANN is load status and the outputs are the transfer capability among the system areas, voltage magnitudes and voltage angles at concerned buses of the areas under consideration. The repeated power flow (RPF method is used in this paper for calculating the power transfer capability, voltage magnitudes and voltage angles necessary for the generation of input-output patterns for training the proposed MLP neural network. Preliminary investigations on a three area 30-bus system reveal that the proposed model is computationally faster than the conventional method.
An Approach to Calculate the Efficiency for an N-Receiver Wireless Power Transfer System
Thabat Thabet
2015-09-01
Full Text Available A wireless power transfer system with more than one receiver is a realistic proposition for charging multiple devices such as phones and a tablets. Therefore, it is necessary to consider systems with single transmitters and multiple receivers in terms of efficiency. Current offerings only consider single device charging systems. A problem encountered is the efficiency of one receiver can be affected by another because of the mutual inductance between them. In this paper, an efficiency calculation method is presented for a wireless power transfer system with one to N-receivers. The mutual inductance between coils is implicitly calculated for different spatial positions and verified by practical experimentation. The effect of changing parameters, such as resonant frequency, coil size and distance between coils, on the efficiency has been studied. A clarification of the special performance of a wireless power transfer system at a specific point has been presented.
Calculation of Skin Depths and Eddy-Current Power Losses for Magnetic Position Sensors
2000-01-01
We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current ex citation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.
I.V. Domanskyi
2015-08-01
Full Text Available Currently, the cause deterioration of quality rating of electricity on tire traction substations AC can be either how mode of operation of power systems, industrial loads so and the impact of electric traction. The experience of energy surveys show that the loss from flow potential equalization currents in each the third plot between traction substations AC is amount to not less than 250 thousand kW∙h per year. To select the optimum power and places location of the device longitudinal capacitive of compensation and decision other tasks it is necessary methodology of systems of calculation that takes into account the complex nature of the mutual influence of the quality of the electricity coming from the energy system of and the transportation process. In the paper proposed three options for calculation algorithms modes work of existing and perspective systems, traction power supply AC jointly with power supply their by energy systems, including the algorithm for calculating networks of different nominal voltages using the transformations; decomposition and synthesis of networks with different voltage levels; the iterations and probabilistic assessment of the impact of power mains. Developed the schemes formalization of graphs and the matrices of portions of the outer and traction power supply and method of selecting parameters and places location of the devices longitudinal capacitive of compensation, which are based on direct methods solving systems of linear algebraic equations with a dense banded and profile-sparse the matrix. Are generalized ways of formation and transformation of graphs of schemes traction power supply and feeding them energy systems and proposed the method of calculation the complex the moment of schemes, which increases the accuracy of calculating of flows power on traction networks to 1-2 % and allows you to select the optimal parameters and places location of the devices longitudinal capacitive of compensation
Calculation and comparison of circuit breaker parameters in Power World Simulator
Kuljinder Kaur,
2016-01-01
Full Text Available A circuit breaker has ratings that an engineer uses for their application. These ratings define circuit breaker performance characteristics. A good understanding of Ratings allow the electrical engineer to make a proper comparison of various circuit breaker designs. In this research work, the different ratings of circuit breaker were calculated. The other objective of this work was comparison between ratings of existing circuit breaker and calculated ratings in POWER WORLD SIMULATOR. Further, the impact of time delay in circuit breaker was studied. These calculations were performed for rated current of 400 & 630 Amps. The results performed in POWER WORLD SIMULATOR were shown better and information gained from the analysis can be used for proper relay selection, settings, performances and coordination.
V. N. Radkevich
2016-01-01
Full Text Available The indicators of power consumption of lighting devices based on LEDs are studied depending on the supplied voltage. For the lamp and floodlight with LEDs active and reactive power, current and power factor as a function of voltage (which value changed in the range 200–245 V were experimentally determined. The analysis of experimental data demonstrated that due to the drivers in the specified voltage range the active power consumed by light devices remains practically unchanged. The reactive power of LED devices depends on the supplied voltage and is capacitive in its nature. In contrast with gas-discharge light sources the LED devices under study do not consume reactive power, but generate it. With the change of the supplied voltage from 200 to 245 V the value of the generated reactive power increases to 60 % for the floodlight and 50 % for the lamp. The LED floodlight has a low coefficient of active power. The current consumed by the floodlight has increased by 22 %, and by the lamp – by 13 %. The formulas for determining the maximum value of the length of the calculated section of single-phase group lines were developed, taking into account specific source data. LED light sources tend to feed by electric power by single-phase group lines. The number of lamps connected to single-phase lines is regulated by normative documents. Bearing this in mind as well as the small power of LED sources single-phase group lines are usually performed with conductors of the smallest possible cross section. The limit values of the length of the calculated section that correspond to a predetermined loss of voltage in line with ambient temperature from 15 to 60 °С were determined for them. The calculations demonstrated that for group lines that feed the LEDs, the choice of conductor cross-sections in accordance with permissible voltage loss is not critical. The determinant factor for the choice of the cross-section of the conductors of group electrical
A web application for sample size and power calculation in case-control microbiome studies.
Mattiello, Federico; Verbist, Bie; Faust, Karoline; Raes, Jeroen; Shannon, William D; Bijnens, Luc; Thas, Olivier
2016-07-01
: When designing a case-control study to investigate differences in microbial composition, it is fundamental to assess the sample sizes needed to detect an hypothesized difference with sufficient statistical power. Our application includes power calculation for (i) a recoded version of the two-sample generalized Wald test of the 'HMP' R-package for comparing community composition, and (ii) the Wilcoxon-Mann-Whitney test for comparing operational taxonomic unit-specific abundances between two samples (optional). The simulation-based power calculations make use of the Dirichlet-Multinomial model to describe and generate abundances. The web interface allows for easy specification of sample and effect sizes. As an illustration of our application, we compared the statistical power of the two tests, with and without stratification of samples. We observed that statistical power increases considerably when stratification is employed, meaning that less samples are needed to detect the same effect size with the same power. The web interface is written in R code using Shiny (RStudio Inc., 2016) and it is available at https://fedematt.shinyapps.io/shinyMB The R code for the recoded generalized Wald test can be found at https://github.com/mafed/msWaldHMP CONTACT: Federico.Mattiello@UGent.be. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
The control of aniseikonia after intraocular lens implantation.
Hillman, J S; Hawkswell, A
1985-01-01
This paper reports a study of postoperative refraction and eikonometry of 50 patients who had unilateral cataract extraction with implantation of a pupil-supported intraocular lens. The mean postoperative aniseikonia (+/- SD) was 1.97 (+/- 1.82). A statistically significant relationship was shown between anisometropia and aniseikonia. Despite aniseikonia of up to 7.8 per cent there were no diplopia problems as the visual system exhibits a high degree of tolerance. It is concluded that aniseikonia can be controlled to within clinically acceptable limits by the simple calculation of intraocular lens power for isometropia.
The calculation of proton and secondary electron stopping powers in liquid water.
Marouane, Abdelhak; Inchaouh, Jamal; Ouaskit, Said; Fathi, Ahmed
2012-07-01
The stopping power of energetic protons in liquid water has been calculated using a new model based on different theoretical and semi-empirical approaches. In this model, we consider the relativistic corrections along with the electronic and nuclear stopping power. The present work accounts for the different interactions made with electrons and nuclei inside the target. Interactions of the incident particle with the target's electrons dominate in the high energy regime; in the low energy regime, the interactions of the projectile with the target nuclei contribute importantly and are included in the calculation. We also compute the stopping cross sections and the stopping power of secondary electrons ejected from proton and hydrogen ionization impact, and generated by hydrogen electron loss processes. The consideration of secondary electrons' stopping power can contribute to the study of nano-dosimetry. Our results are in good agreement with existing experimental data. This calculation model can be useful for different applications in medical physics and space radiation health, such as hadron therapy for cancer treatment or radiation protection for astronauts.
Analysis of offsite dose calculation methodology for a nuclear power reactor
Moser, Donna Smith [Univ. of North Carolina, Chapel Hill, NC (United States)
1995-01-01
This technical study reviews the methodology for calculating offsite dose estimates as described in the offsite dose calculation manual (ODCM) for Pennsylvania Power and Light - Susquehanna Steam Electric Station (SSES). An evaluation of the SSES ODCM dose assessment methodology indicates that it conforms with methodology accepted by the US Nuclear Regulatory Commission (NRC). Using 1993 SSES effluent data, dose estimates are calculated according to SSES ODCM methodology and compared to the dose estimates calculated according to SSES ODCM and the computer model used to produce the reported 1993 dose estimates. The 1993 SSES dose estimates are based on the axioms of Publication 2 of the International Commission of Radiological Protection (ICRP). SSES Dose estimates based on the axioms of ICRP Publication 26 and 30 reveal the total body estimates to be the most affected.
Computer program for calculating flow parameters and power requirements for cryogenic wind tunnels
Dress, D. A.
1985-01-01
A computer program has been written that performs the flow parameter calculations for cryogenic wind tunnels which use nitrogen as a test gas. The flow parameters calculated include static pressure, static temperature, compressibility factor, ratio of specific heats, dynamic viscosity, total and static density, velocity, dynamic pressure, mass-flow rate, and Reynolds number. Simplifying assumptions have been made so that the calculations of Reynolds number, as well as the other flow parameters can be made on relatively small desktop digital computers. The program, which also includes various power calculations, has been developed to the point where it has become a very useful tool for the users and possible future designers of fan-driven continuous-flow cryogenic wind tunnels.
Calculation of power consumption and induced heat for EMC aluminum ingots
无
2001-01-01
The electrical parameters and power consumption in electromagnetic casting of aluminum ingots were calculated and discussed in detail. Moreover, the induced heat was calculated with the eddy current within the liquid column. It is found that the calculated values agree with the measured results. Once the inductor current was given, the magnetic flux density in electromagnetic casting could be calculated and the electromagnetic pressure could be obtained. The key to the EMC is the balance between the electromagnetic pressure and the metallostatic pressure. As the liquid column, controlled by the casting speed and pouring speed through a magnetic sensor, is kept away from the inductor, a gap forms linear relationship between the inductor and ingot. The bigger the current is, the smaller the ingot size is.
O'Neill, Mark; Howell, Joe; Fikes, John; Fork, Richard; Phillips, Dane; Aiken, Dan; McDanal, A. J.
2006-01-01
For the past 2% years, our team has been developing a unique photovoltaic concentrator array for collection and conversion of infrared laser light. This laser-receiving array has evolved from the solar-receiving Stretched Lens Array (SLA). The laser-receiving version of SLA is being developed for space power applications when or where sunlight is not available (e.g., the eternally dark lunar polar craters). The laser-receiving SLA can efficiently collect and convert beamed laser power from orbiting spacecraft or other sources (e.g., solar-powered lasers on the permanently illuminated ridges of lunar polar craters). A dual-use version of SLA can produce power from sunlight during sunlit portions of the mission, and from beamed laser light during dark portions of the mission. SLA minimizes the cost and mass of photovoltaic cells by using gossamer-like Fresnel lenses to capture and focus incoming light (solar or laser) by a factor of 8.5X, thereby providing a cost-effective, ultra-light space power system.
Incorrect calculation of power outputs masks the ergogenic capacity of creatine supplementation.
Havenetidis, Konstadinos; Cooke, Carlton B; Butterly, Ron; King, Roderick F G J
2006-10-01
This study assessed the effect of incorrect calculation of power output measurement on the ergogenic properties of creatine. Fifteen males performed repeated Wingate anaerobic tests, under baseline, placebo, and creatine conditions. Statistics showed significant differences (p supplemented conditions compared with placebo conditions, whereas no significant differences existed between the baseline and placebo conditions. However, the performance enhancement effect of creatine became significant only when the corrected (for the inertia of the flywheel) method was employed for measuring peak and minimum power. Mean (+/- SD) values across all cycle sprints for placebo versus creatine were 1033 +/- 100 W versus 1130 +/- 95 W for peak power and 385 +/- 78 W versus 427 +/- 70 W for minimum power. No significant differences were shown using the uncorrected method for peak power (756 +/- 97 W versus 786 +/- 88 W) and minimum power 440 +/- 64 W pre versus 452 +/- 65 W post). In conclusion, the present study suggests that the potentiating effect of creatine might be underestimated if the inertial effects of the flywheel are not considered in power output determination.
Efficient Computation of Power, Force, and Torque in BEM Scattering Calculations
Reid, M T Homer
2013-01-01
We present concise, computationally efficient formulas for several quantities of interest -- including absorbed and scattered power, optical force (radiation pressure), and torque -- in scattering calculations performed using the boundary-element method (BEM) [also known as the method of moments (MOM)]. Our formulas compute the quantities of interest \\textit{directly} from the BEM surface currents with no need ever to compute the scattered electromagnetic fields. We derive our new formulas and demonstrate their effectiveness by computing power, force, and torque in a number of example geometries. Free, open-source software implementations of our formulas are available for download online.
Calculation Metho d of Power Law Fluid Equivalent Permeability Considering Capillary Shap e
YANG Er-long; LI Huan; GAO Hui-juan; GU Ting-ting
2015-01-01
While studying the flow of oil and gas in the reservoir, it is not realistic that capillary with circular section is only used to express the pores. It is more representative to simulate porous media pore with kinds of capillary with triangle or rectangle section etc. In the condition of the same diameter, when polymer for oil displacement flows in the porous medium, there only exists shear flow which can be expressed with power law model. Based on fluid flow-pressure drop equation in single capillary, this paper gives a calculation method of equivalent permeability of power law fluid of single capillary and capillary bundles with different sections.
Xia Hua
2013-10-01
Full Text Available AIM: To assess the refractive outcome of clear lensectomy combined with piggyback intraocular lens implantation in highly hyperopic patients.METHODS: This case review included 19 eyes of 10 patients with high hyperopia and axial length less than 21mm. Intraocular lens power was calculated for emmetropia using the Holladay II formula in 17 eyes, and SRK/T formula in 2 eyes following clear lens extraction and piggyback intraocular lens implantation. Patients were examined periodically over 24 months for visual acuity and spherical equivalent (SE.RESULTS: The mean postoperative SE at 24 months was 0.20±1.39D (range, -3.00 to 2.50D, better than preoperative 9.81±2.62D (range, +6.00 to +14.50D (PPP=0.34. Twelve eyes maintained and 1 gained 1 or more Snellen line of BCVA, 4 eyes lost 1 line, and 2 eyes lost 2 lines at 24 postoperative months. Twelve eyes best-corrected near visual acuity (BCNVA achieved J1 at postoperative 24 months compared to preoperative 7 eyes and the other 7 eyes better than J3.CONCLUSION: Clear lens extraction combined piggyback intraocular lens implantation appears to be an effective procedure to correct high hyperopia but mild overcorrection and intralenticular opacification may require secondary procedure.
USING TIME VARIANT VOLTAGE TO CALCULATE ENERGY CONSUMPTION AND POWER USE OF BUILDING SYSTEMS
Makhmalbaf, Atefe; Augenbroe , Godfried
2015-12-09
Buildings are the main consumers of electricity across the world. However, in the research and studies related to building performance assessment, the focus has been on evaluating the energy efficiency of buildings whereas the instantaneous power efficiency has been overlooked as an important aspect of total energy consumption. As a result, we never developed adequate models that capture both thermal and electrical characteristics (e.g., voltage) of building systems to assess the impact of variations in the power system and emerging technologies of the smart grid on buildings energy and power performance and vice versa. This paper argues that the power performance of buildings as a function of electrical parameters should be evaluated in addition to systems’ mechanical and thermal behavior. The main advantage of capturing electrical behavior of building load is to better understand instantaneous power consumption and more importantly to control it. Voltage is one of the electrical parameters that can be used to describe load. Hence, voltage dependent power models are constructed in this work and they are coupled with existing thermal energy models. Lack of models that describe electrical behavior of systems also adds to the uncertainty of energy consumption calculations carried out in building energy simulation tools such as EnergyPlus, a common building energy modeling and simulation tool. To integrate voltage-dependent power models with thermal models, the thermal cycle (operation mode) of each system was fed into the voltage-based electrical model. Energy consumption of systems used in this study were simulated using EnergyPlus. Simulated results were then compared with estimated and measured power data. The mean square error (MSE) between simulated, estimated, and measured values were calculated. Results indicate that estimated power has lower MSE when compared with measured data than simulated results. Results discussed in this paper will illustrate the
Hypothesis testing and power calculations for taxonomic-based human microbiome data.
Patricio S La Rosa
Full Text Available This paper presents new biostatistical methods for the analysis of microbiome data based on a fully parametric approach using all the data. The Dirichlet-multinomial distribution allows the analyst to calculate power and sample sizes for experimental design, perform tests of hypotheses (e.g., compare microbiomes across groups, and to estimate parameters describing microbiome properties. The use of a fully parametric model for these data has the benefit over alternative non-parametric approaches such as bootstrapping and permutation testing, in that this model is able to retain more information contained in the data. This paper details the statistical approaches for several tests of hypothesis and power/sample size calculations, and applies them for illustration to taxonomic abundance distribution and rank abundance distribution data using HMP Jumpstart data on 24 subjects for saliva, subgingival, and supragingival samples. Software for running these analyses is available.
POPCYCLE: a computer code for calculating nuclear and fossil plant levelized life-cycle power costs
Hardie, R.W.
1982-02-01
POPCYCLE, a computer code designed to calculate levelized life-cycle power costs for nuclear and fossil electrical generating plants is described. Included are (1) derivations of the equations and a discussion of the methodology used by POPCYCLE, (2) a description of the input required by the code, (3) a listing of the input for a sample case, and (4) the output for a sample case.
Nash, Ulrik William
2014-01-01
Firms consist of people who make decisions to achieve goals. How do these people develop the expectations which underpin the choices they make? The lens model provides one answer to this question. It was developed by cognitive psychologist Egon Brunswik (1952) to illustrate his theory of probabil......Firms consist of people who make decisions to achieve goals. How do these people develop the expectations which underpin the choices they make? The lens model provides one answer to this question. It was developed by cognitive psychologist Egon Brunswik (1952) to illustrate his theory...... of probabilistic functionalism, and concerns the environment and the mind, and adaptation by the latter to the former. This entry is about the lens model, and probabilistic functionalism more broadly. Focus will mostly be on firms and their employees, but, to fully appreciate the scope, we have to keep in mind...
Calculation of the Power Peaking Factor Using CFNN and Its Uncertainty Analysis
Back, Ju Hyun; Kim, Dong Yeong; Yoo, Kwae Hwan; Choi, Geon Pil; Na, Man Gyun [Chosun University, Gwangju (Korea, Republic of)
2016-05-15
The local power density (LPD) and DNBR must be calculated in order to perform the main functions of the core protection calculator (CPC) and the core operation limit supervisory system (COLSS). CPC and COLSS play a role in the protection and monitoring systems of the optimized power reactor 1000 (OPR1000) and the advanced power reactor 1400 (APR1400). LPD should be estimated accurately to prevent fuel rods from melting. LPD at the hottest part of the core is called the power peaking factor (PPF, F{sub q} ). LPD at the hottest part of the core is more important than LPD at any other position in a reactor core. DNBR and PPF are the most important factors that must be continuously monitored from a safety aspect. The aim of the study is to calculate PPF in a reactor core by a cascaded fuzzy neural networks (CFNN) model according to operating conditions. The operation condition is reactor power, core inlet temperature, pressurizer pressure, mass flowrate, axial shape index (ASI), and variety of control rod position. The proposed CFNN model that is a PPF estimation algorithm is verified by using the nuclear and thermal data acquired from numerical simulations of OPR1000. The CFNN regression models were optimized by using the data set prepared as training data and tested by using verification data. The developed CFNN models were applied to the OPR 1000. As a result, the RMS error of the estimated PPF values is below 0.05%. In addition, their uncertainty was analyzed by a bootstrap method using 100 sampled development data sets.
Power and sample size calculations for Mendelian randomization studies using one genetic instrument.
Freeman, Guy; Cowling, Benjamin J; Schooling, C Mary
2013-08-01
Mendelian randomization, which is instrumental variable analysis using genetic variants as instruments, is an increasingly popular method of making causal inferences from observational studies. In order to design efficient Mendelian randomization studies, it is essential to calculate the sample sizes required. We present formulas for calculating the power of a Mendelian randomization study using one genetic instrument to detect an effect of a given size, and the minimum sample size required to detect effects for given levels of significance and power, using asymptotic statistical theory. We apply the formulas to some example data and compare the results with those from simulation methods. Power and sample size calculations using these formulas should be more straightforward to carry out than simulation approaches. These formulas make explicit that the sample size needed for Mendelian randomization study is inversely proportional to the square of the correlation between the genetic instrument and the exposure and proportional to the residual variance of the outcome after removing the effect of the exposure, as well as inversely proportional to the square of the effect size.
A.V. Erisov
2016-05-01
Full Text Available Purpose. Simplification of accounting ratio to determine the magnetic field strength of electric power lines, and assessment of their environmental safety. Methodology. Description of the transmission lines of the magnetic field by using techniques of spatial harmonic analysis in the cylindrical coordinate system is carried out. Results. For engineering calculations of electric power lines magnetic field with sufficient accuracy describes their first spatial harmonic magnetic field. Originality. Substantial simplification of the definition of the impact of the construction of transmission line poles on the value of its magnetic field and the bands of land alienation sizes. Practical value. The environmentally friendly projection electric power lines on the level of the magnetic field.
Nash, Ulrik William
2014-01-01
Firms consist of people who make decisions to achieve goals. How do these people develop the expectations which underpin the choices they make? The lens model provides one answer to this question. It was developed by cognitive psychologist Egon Brunswik (1952) to illustrate his theory of probabil......Firms consist of people who make decisions to achieve goals. How do these people develop the expectations which underpin the choices they make? The lens model provides one answer to this question. It was developed by cognitive psychologist Egon Brunswik (1952) to illustrate his theory...
Calculating magnetic shielding effectiveness for high-power dc comparator by magnetic circuit method
WANG Xiao-wei; REN Shi-yan
2007-01-01
Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comparators when an external radial magnetic field is added. The mathematical relationship between the magnetic shielding effectiveness and the parameters of the magnetic shielding body were obtained. To verify the validity of the calculation method, we developped a procedure to measure the magnetic shielding effectiveness of the magnetic body by measuring the induction voltage of the detection winding instead of the magnetic intensity at a point in the magnetic shielding body, making the manipulation much easier. The result calculated with the magnetic circuit method turns out to be closer to the measured one compared with that calculated with a conventional algorithm proposed by Ren, suggesting that the magnetic circuit method is an applicable tool for estimating the toroidal cavity magnetic shielding effectiveness of a heavy current comparator when a radial magnetic field is added.
Charged Particle Stopping Power Effects on Ignition: Some Results from an Exact Calculation
Singleton, Robert L
2007-01-01
A completely rigorous first-principles calculation of the charged particle stopping power has recently been performed by Brown, Preston, and Singleton (BPS). This calculation is exact to leading and next-to-leading order in the plasma number density, including an exact treatment of two-body quantum scattering. The BPS calculation is therefore extremely accurate in the plasma regime realized during the ignition and burn of an inertial confinement fusion capsule. For deuterium-tritium fusion, the 3.5 MeV alpha particle range tends to be 20-30% longer than most models in the literature have predicted, and the energy deposition into the ions tends to be smaller. Preliminary numerical simulations indicate that this increases the rho-R required to achieve ignition.
Reference neutron transport calculation note for Korea nuclear power plants with 3-loop PWR reactors
Kim, Byung Cheol; Chang, Ki Oak
1997-05-01
Reactor pressure vessel (RPV) steels are subjected to neutron irradiation at a temperature of about 290 deg C. This radiation exposure alters the mechanical properties, leading to a shift of the brittle-to-ductile transition temperature toward higher temperatures and to a diminution of the rupture energy as determined by Charpy V-notch tests. This radiation embrittlement is one of the important aging factors of nuclear power plants. U.S. NRC recommended the basic requirements for the determination of the pressure vessel fluence by regulatory guide DG-1025 in order to reduce the uncertainty in the determination of neutron fluence calculation and measurements. The determination of the pressure vessel fluence is based on both calculations and measurements. The fluence prediction is made with a calculation and the measurements are used to qualify the calculational methodology. Because of the importance and the difficulty of these calculations, the method`s qualification by comparison to measurement must be made to ensure a reliable and accurate vessel fluence determination. This reference calculation note is to provide a series of forward and adjoint neutron transport calculations for use in the evaluation of neutron dosimetry from surveillance capsule irradiations at 3-loop PWR reactor as well as for use in the determination of the neutron exposure of the reactor vessel wall in accordance with U.S Regulatory Guide DG-1025 requirements. The calculations of the pressure vessel fluence consist of the following steps; (1) Determination of the geometrical and material input data, (2) Determination of the core neutron source, and (3) Propagation of the neutron fluence from the core to the vessel and into the cavity. (author). 12 tabs., 3 figs., 7 refs.
Reich, Nicholas G; Myers, Jessica A; Obeng, Daniel; Milstone, Aaron M; Perl, Trish M
2012-01-01
In recent years, the number of studies using a cluster-randomized design has grown dramatically. In addition, the cluster-randomized crossover design has been touted as a methodological advance that can increase efficiency of cluster-randomized studies in certain situations. While the cluster-randomized crossover trial has become a popular tool, standards of design, analysis, reporting and implementation have not been established for this emergent design. We address one particular aspect of cluster-randomized and cluster-randomized crossover trial design: estimating statistical power. We present a general framework for estimating power via simulation in cluster-randomized studies with or without one or more crossover periods. We have implemented this framework in the clusterPower software package for R, freely available online from the Comprehensive R Archive Network. Our simulation framework is easy to implement and users may customize the methods used for data analysis. We give four examples of using the software in practice. The clusterPower package could play an important role in the design of future cluster-randomized and cluster-randomized crossover studies. This work is the first to establish a universal method for calculating power for both cluster-randomized and cluster-randomized clinical trials. More research is needed to develop standardized and recommended methodology for cluster-randomized crossover studies.
Transferring Lens Prescriptions Between Lens-Design Programs
Stacy, John E.; Wooley, Laura; Carlin, Brian
1989-01-01
Optical Lens Prescription Data Formatter computer program enables user to transfer complicated lens prescriptions quickly and easily from one major optical-design program to another and back again. One can take advantage of inherent strength of either program. Programs are ACCOS V from Scientific Calculations, Inc., of Fishers, NY, and CODE V from Optical Research Associates of Pasadena, CA. VAX version written in FORTRAN.
Tian, Jiandong; Duan, Zhigang; Ren, Weihong; Han, Zhi; Tang, Yandong
2016-04-04
The spectral power distributions (SPD) of outdoor light sources are not constant over time and atmospheric conditions, which causes the appearance variation of a scene and common natural illumination phenomena, such as twilight, shadow, and haze/fog. Calculating the SPD of outdoor light sources at different time (or zenith angles) and under different atmospheric conditions is of interest to physically-based vision. In this paper, for computer vision and its applications, we propose a feasible, simple, and effective SPD calculating method based on analyzing the transmittance functions of absorption and scattering along the path of solar radiation through the atmosphere in the visible spectrum. Compared with previous SPD calculation methods, our model has less parameters and is accurate enough to be directly applied in computer vision. It can be applied in computer vision tasks including spectral inverse calculation, lighting conversion, and shadowed image processing. The experimental results of the applications demonstrate that our calculation methods have practical values in computer vision. It establishes a bridge between image and physical environmental information, e.g., time, location, and weather conditions.
Ground moving target signal model and power calculation in forward scattering micro radar
LONG Teng; HU Cheng; MIKHAIL Cherniakov
2009-01-01
Forward scattering micro radar is used for situation awareness;its operational range is relatively short because of the battery power and local horizon,the free space propagation model is not appropriate.The ground moving targets,such as humans,cars and tanks,have only comparable size with the transmitted signal wavelength;the point target model and the linear change of observation angle are not applicable.In this paper,the signal model of ground moving target is developed based on the case of forward scattering micro radar,considering the two-ray propagation model and area target model,and nonlinear change of observation angle as well as high order phase error.Furthermore,the analytical form of the received power from moving target has been obtained.Using the simulated forward scattering radar cross section,the received power of theoretical calculation is near to that of measured data.In addition,the simulated signal model of ground moving target is perfectly matched with the experimented data.All these results show the correctness of analytical calculation completely.
Animation model of Krsko nuclear power plant for RELAP5 calculations
Prosek, Andrej, E-mail: andrej.prosek@ijs.s [Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Mavko, Borut [Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia)
2011-04-15
Today most software applications, also in the nuclear field, come with a graphical user interface. The first graphical user interface for the RELAP5 thermal-hydraulic computer code was called the Nuclear Plant Analyzer (NPA). Later, Symbolic Nuclear Analysis Package (SNAP) was developed. The purpose of the present study was to develop SNAP animation model of Krsko nuclear power plant (NPP) for RELAP5 calculations with the aim to help analyze the results. In addition, the reference calculations for Krsko full scope simulator validation were performed with the latest RELAP5/MOD3.3 Patch 03 code and compared to previous RELAP5 versions to provide verified source data, needed to demonstrate animation model. In total six scenarios were analyzed: two scenarios of the small-break loss-of-coolant accident, two scenarios of the loss of main feedwater, a scenario of the anticipated transient without scram, and a scenario of the steam generator tube rupture. The use of SNAP for animation of Krsko nuclear power plant analyses showed several benefits, especially better understanding of the calculated physical phenomena and processes. It can be concluded that an animation tool was created, which enables to analyze very complex accident scenarios. The graphical surface helps keeping the overview and focusing on the main influences. Also, the use of such support tools to system codes may significantly contribute to better quality of safety analysis.
A Mexican Hat with holes: calculating low resolution power spectra from data with gaps
Arevalo, P; Zhuravleva, I; Hernandez-Monteagudo, C; Revnivtsev, M
2012-01-01
A simple method for calculating a low-resolution power spectrum from data with gaps is described. The method is a modification of the $\\Delta$-variance method previously described by Stutzki and Ossenkopf. A Mexican Hat filter is used to single out fluctuations at a given spatial scale and the variance of the convolved image is calculated. The gaps in the image, defined by the mask, are corrected for by representing the Mexican Hat filter as a difference between two Gaussian filters with slightly different widths, convolving the image and mask with these filters and dividing the results before calculating the final filtered image. This method cleanly compensates for data gaps even if these have complicated shapes and cover a significant fraction of the data. The method was developed to deal with problematic 2D images, where irregular detector edges and masking of contaminating sources compromise the power spectrum estimates, but it can also be straightforwardly applied to 1D timing analysis or 3D data cubes f...
Improvement of Power Flow Calculation with Optimization Factor Based on Current Injection Method
Lei Wang
2014-01-01
Full Text Available This paper presents an improvement in power flow calculation based on current injection method by introducing optimization factor. In the method proposed by this paper, the PQ buses are represented by current mismatches while the PV buses are represented by power mismatches. It is different from the representations in conventional current injection power flow equations. By using the combined power and current injection mismatches method, the number of the equations required can be decreased to only one for each PV bus. The optimization factor is used to improve the iteration process and to ensure the effectiveness of the improved method proposed when the system is ill-conditioned. To verify the effectiveness of the method, the IEEE test systems are tested by conventional current injection method and the improved method proposed separately. Then the results are compared. The comparisons show that the optimization factor improves the convergence character effectively, especially that when the system is at high loading level and R/X ratio, the iteration number is one or two times less than the conventional current injection method. When the overloading condition of the system is serious, the iteration number in this paper appears 4 times less than the conventional current injection method.
CATARACT: Computer code for improving power calculations at NREL's high-flux solar furnace
Scholl, K.; Bingham, C.; Lewandowski, A.
1994-01-01
The High-Flux Solar Furnace (HFSF), operated by the National Renewable Energy Laboratory, uses a camera-based, flux-mapping system to analyze the distribution and to determine total power at the focal point. The flux-mapping system consists of a diffusively reflecting plate with seven circular foil calorimeters, a charge-coupled device (CCD) camera, an IBM-compatible personal computer with a frame-grabber board, and commercial image analysis software. The calorimeters provide flux readings that are used to scale the image captured from the plate by the camera. The image analysis software can estimate total power incident on the plate by integrating under the 3-dimensional image. Because of the physical layout of the HFSF, the camera is positioned at a 20 angle to the flux mapping plate normal. The foreshortening of the captured images that results represents a systematic error in the power calculations because the software incorrectly assumes the image is parallel to the camera's array. We have written a FORTRAN computer program called CATARACT (camera/target angle correction) that we use to transform the original flux-mapper image to a plane that is normal to the camera's optical axis. A description of the code and the results of experiments performed to verify it are presented. Also presented are comparisons of the total power available from the HFSF as determined from the flux mapping system and theoretical considerations.
An equivalent circuit model and power calculations for the APS SPX crab cavities.
Berenc, T. (Accelerator Systems Division (APS))
2012-03-21
An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.
Kim, Seung Jun [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-07-17
The current study aims to predict the steady state power of a generic solution vessel and to develop a corresponding heat transfer coefficient correlation for a Moly99 production facility by conducting a fully coupled multi-physics simulation. A prediction of steady state power for the current application is inherently interconnected between thermal hydraulic characteristics (i.e. Multiphase computational fluid dynamics solved by ANSYS-Fluent 17.2) and the corresponding neutronic behavior (i.e. particle transport solved by MCNP6.2) in the solution vessel. Thus, the development of a coupling methodology is vital to understand the system behavior at a variety of system design and postulated operating scenarios. In this study, we report on the k-effective (keff) calculation for the baseline solution vessel configuration with a selected solution concentration using MCNP K-code modeling. The associated correlation of thermal properties (e.g. density, viscosity, thermal conductivity, specific heat) at the selected solution concentration are developed based on existing experimental measurements in the open literature. The numerical coupling methodology between multiphase CFD and MCNP is successfully demonstrated, and the detailed coupling procedure is documented. In addition, improved coupling methods capturing realistic physics in the solution vessel thermal-neutronic dynamics are proposed and tested further (i.e. dynamic height adjustment, mull-cell approach). As a key outcome of the current study, a multi-physics coupling methodology between MCFD and MCNP is demonstrated and tested for four different operating conditions. Those different operating conditions are determined based on the neutron source strength at a fixed geometry condition. The steady state powers for the generic solution vessel at various operating conditions are reported, and a generalized correlation of the heat transfer coefficient for the current application is discussed. The assessment of multi
Huang, Yong; Zhang, Kang; Kang, Jin U.; Calogero, Don; James, Robert H.; Ilev, Ilko K.
2011-12-01
We propose a novel common-path Fourier domain optical coherence tomography (CP-FD-OCT) method for noncontact, accurate, and objective in vitro measurement of the dioptric power of intraocular lenses (IOLs) implants. The CP-FD-OCT method principle of operation is based on simple two-dimensional scanning common-path Fourier domain optical coherence tomography. By reconstructing the anterior and posterior IOL surfaces, the radii of the two surfaces, and thus the IOL dioptric power are determined. The CP-FD-OCT design provides high accuracy of IOL surface reconstruction. The axial position detection accuracy is calibrated at 1.22 μm in balanced saline solution used for simulation of in situ conditions. The lateral sampling rate is controlled by the step size of linear scanning systems. IOL samples with labeled dioptric power in the low-power (5D), mid-power (20D and 22D), and high-power (36D) ranges under in situ conditions are tested. We obtained a mean power of 4.95/20.11/22.09/36.25 D with high levels of repeatability estimated by a standard deviation of 0.10/0.18/0.2/0.58 D and a relative error of 2/0.9/0.9/1.6%, based on five measurements for each IOL respectively. The new CP-FD-OCT method provides an independent source of IOL power measurement data as well as information for evaluating other optical properties of IOLs such as refractive index, central thickness, and aberrations.
Xiaohong Guo
2014-01-01
Full Text Available Purpose. To evaluate 2-year visual acuities and questionnaire after bilateral implantation of SN6AD1 multifocal intraocular lens (MIOL or SN60WF IOL. Methods. Patients randomly scheduled for bilateral implantation of SN6AD1 MIOL and SN60WF IOL with 2-year follow-up were enrolled. Uncorrected/corrected distance and near visual acuity, uncorrected intermediate visual acuity at 63 cm under high and low contrast, reading activity, the defocus curve, and a quality-of-life questionnaire were evaluated. Results. Each group comprised 20 patients. Uncorrected intermediate visual acuities and uncorrected near visual acuity were better in SN6AD1 group than in SN60WF group (P=0.005, P=0.011, and P<0.001. In SN6AD1 group, the uncorrected intermediate and near visual acuities 1 year and 2 years postoperatively were reduced than postoperative 3-month outcomes, respectively. SN6AD1 group reported superior overall spectacle independence and inferior satisfaction. SN6AD1 group had a longer reading newspaper duration than SN60WF group (P=0.036. When using mobile phone, SN6AD1 group had a more comfortable distance than SN60WF group (P<0.001 and higher speed of reading fixed text message (P<0.001. Conclusion. SN6AD1 MIOL provided a satisfactory full range of visual acuities and questionnaire performance 2 years postoperatively. One-year and 2-year uncorrected near and intermediate visual acuities of SN6AD1 MIOL were lower than those 3 months postoperatively.
吴羽; 龙晓莉; 焦中兴; 何广源; 张倩
2015-01-01
In order to obtain 1064nm laser with high power and high beam quality , a laser resonator was designed to solve thermal lens effect with a concave lens as compensation lens .The selection of the compensation lens was analyzed .A Nd∶YAG laser with a compensation lens and a plano-plano cavity was verified in the experiment .High beam quality 55W 1064nm laser was obtained when the focal length of the concave lens was 250mm and the transmittance of the output mirror was 30%.This research is helpful to the design of laser resonators with high power and beam quality .%为了获得高功率、高光束质量的1064nm激光，采用凹透镜作为补偿透镜来补偿激光棒的热透镜效应。对补偿透镜的选取进行理论分析，并使用所设计的包含补偿透镜的平平谐振腔Nd∶YAG激光器进行了实验验证。在实验中，使用焦距为250mm的凹透镜、透过率为30％的输出耦合镜，获得了55W 的高功率、高光束质量的1064nm激光输出。结果表明，此项研究对高功率、高光束质量激光器谐振腔的设计是有帮助的。
Initial RattleSnake Calculations of the Hot Zero Power BEAVRS
M. Ellis; J. Ortensi; Y. Wang; K. Smith; R.C. Martineau
2014-01-01
The validation of the Idaho National Laboratory's next generation of reactor physics analysis codes is an essential and ongoing task. The validation process requires a large undertaking and includes detailed, realistic models that can accurately predict the behavior of an operational nuclear reactor. Over the past few years the INL has developed the RattleSnake application and supporting tools on the MOOSE framework to perform these reactor physics calculations. RattleSnake solves the linearized Boltzmann transport equation with a variety of solution meth ods. Various traditional reactor physics benchmarks have already been performed, but a more realistic light water reactor comparison was needed to solidify the status of the code and deter mine its fidelity. The INL team decided to use the Benchmark for Evaluation and Validation of Reactor Simulations, which was made available in early 2013. This benchmark is a one of-a-kind document assembled by the Massachusetts Institute of Technology, which includes two cycles of detailed, measured PWR operational data. The results from this initial study of the hot zero power conditions show the current INL analysis procedure with DRAGON4 cross section preparation and using the low order diffusion solver in RattleSnake for the whole core calculations yield very encouraging results for PWR analysis. The radial assembly power distributions, radial detector measurements and control rod worths were computed with good accuracy. The computation of the isothermal temperature coefficients of reactivity require further study.
Wang, Mu; Zhu, Guangzhi; Zhu, Xiao; Feng, Yufan; Gao, Jiapeng
2016-11-01
An numerical model considering solder viscoplasticity is developed to analyze the thermal deformation of laser disk with indium bonded. The characteristic of soft bonding material is described using Anand viscoplasticity model. The Finite Element Method analytical results show that the back surface of laser disk with pumping will deform more significantly with time and finally be steady. Correspondingly the refraction power increase gradually and diffraction loss induced by aspherical aberration decrease gradually. Futhermore when pump spot is larger the refraction power and aspherical aberration will change more due to solder viscoplasticity.
Fast calculation of the maximum power point of photovoltaic generators under partial shading
Carlos Andres Ramos-Paja
2016-09-01
Full Text Available This paper presents a method to calculate the energy production of photovoltaic generators considering partial shading or mismatched conditions. The proposed method is based on the complete one-diode model including the bypass diode in its exponential form, where the current and voltage values of the modules composing the photovoltaic panel array are calculated without using the Lambert-W function. In addition, the method introduces a procedure to calculate the vicinity of the maximum power points, which enables the reduction of the operations required to obtain the global maximum. The proposed method provides short simulation times and high accuracy. On the other hand, since the method does not require complex mathematical functions, it can be implemented straightforwardly on known software packages and development languages such as C and C++. Those characteristics make this method a useful tool to evaluate the economic viability and return-of-investment time of photovoltaic installations. Simulation results and comparisons with a classical procedure confirm the good performance of the proposed method in terms of execution time and accuracy.
Toric intraocular lens orientation and residual refractive astigmatism: an analysis
Potvin R
2016-09-01
Full Text Available Rick Potvin,1 Brent A Kramer,2 David R Hardten,3 John P Berdahl4 1Science in Vision, Akron, NY, 2University of Iowa Carver College of Medicine, Iowa City, IA, 3Minnesota Eye Consultants, Minnetonka, MN, 4Vance Thompson Vision, Sioux Falls, SD, USA Purpose: To analyze intraocular lens (IOL orientation data from an online toric back-calculator (astigmatismfix.com for determining if differences were apparent by lens type.Methods: A retrospective review of astigmatismfix.com toric back-calculations that included IOL identification and intended orientation axis.Results: Of 12,812 total validated calculation records, 8,229 included intended orientation and lens identification data. Of the latter, 5,674 calculations (69% involved lenses oriented 5° or more from their intended position. Using estimated toric lens usage data, the percentage of lenses with orientation ≥5° from intended was 0.89% overall, but the percentage varied significantly between specific toric lens brands (P<0.05. The percentage of back-calculations related to lenses that were not oriented as intended was also statistically significantly different by lens brand (P<0.05. When IOLs were misoriented, they were significantly more likely to be misoriented in a counterclockwise direction (P<0.05. This was found to be due to a bias toward counterclockwise orientation observed with one specific brand, a bias that was not observed with the other three brands analyzed here.Conclusion: The percentage of eyes with lens orientation ≥5° from intended in the Toric Results Analyzer data set was <1% of toric IOLs in general, with the relative percentage of Tecnis® Toric IOLs significantly higher than AcrySof® Toric IOLs. Both of these had higher rates than the Staar® Toric and Trulign® Toric lenses, with the availability of higher Tecnis and AcrySof cylinder powers a likely contributing factor. The AcrySof Toric IOL appears to be less likely than the Tecnis Toric IOL to cause residual
Can manipulation of orthokeratology lens parameters modify peripheral refraction?
Kang, Pauline; Gifford, Paul; Swarbrick, Helen
2013-11-01
To investigate changes in peripheral refraction, corneal topography, and aberrations induced by changes in orthokeratology (OK) lens parameters in myopes. Subjects were fitted with standard OK lenses that were worn overnight for 2 weeks. Peripheral refraction, corneal topography, and corneal surface aberrations were measured at baseline and after 14 nights of OK lens wear. Subsequent to a 2-week washout period, subjects were refitted with another set of lenses where one eye was randomly assigned to wear an OK lens with a smaller optic zone diameter (OZD) and the other eye with a steeper peripheral tangent. Measurements were taken again at a second baseline and after 14 days of overnight wear of the second OK lens set. Standard OK lenses with a 6-mm OZD and 1/4 peripheral tangent caused significant changes in both peripheral refraction and corneal topography. Significant hyperopic shift occurred in the central visual field (VF) while a myopic shift was found at 35 degrees in the nasal VF. OK induced significant reductions in corneal power at all positions along the horizontal corneal chord except at 2.4 mm nasal where there was no significant change and at 2.8 mm nasal where there was an increase in corneal refractive power. A positive shift in spherical aberration was induced for all investigated lens designs except for the 1/2 tangent design when calculated over a 4-mm pupil. Reducing OZD and steepening the peripheral tangent did not cause significant changes in peripheral refraction or corneal topography profiles across the horizontal meridian. OK lenses caused significant changes in peripheral refraction, corneal topography, and corneal surface aberrations. Modifying OZD and peripheral tangent made no significant difference to the peripheral refraction or corneal topography profile. Attempting to customize refraction and topography changes through manipulation of OK lens parameters appears to be a difficult task.
Shao, Quanxi; Wang, You-Gan
2009-09-01
Power calculation and sample size determination are critical in designing environmental monitoring programs. The traditional approach based on comparing the mean values may become statistically inappropriate and even invalid when substantial proportions of the response values are below the detection limits or censored because strong distributional assumptions have to be made on the censored observations when implementing the traditional procedures. In this paper, we propose a quantile methodology that is robust to outliers and can also handle data with a substantial proportion of below-detection-limit observations without the need of imputing the censored values. As a demonstration, we applied the methods to a nutrient monitoring project, which is a part of the Perth Long-Term Ocean Outlet Monitoring Program. In this example, the sample size required by our quantile methodology is, in fact, smaller than that by the traditional t-test, illustrating the merit of our method.
Guerrero, A. F.; Mesa, J.
2016-07-01
Because of the behavior that charged particles have when they interact with biological material, proton therapy is shaping the future of radiation therapy in cancer treatment. The planning of radiation therapy is made up of several stages. The first one is the diagnostic image, in which you have an idea of the density, size and type of tumor being treated; to understand this it is important to know how the particles beam interacts with the tissue. In this work, by using de Lindhard formalism and the Y.R. Waghmare model for the charge distribution of the proton, the electronic stopping power (SP) for a proton beam interacting with a liquid water target in the range of proton energies 101 eV - 1010 eV taking into account all the charge states is calculated.
Сombined Calculation of Electric Power Technical Losses in 0,38–10 kV Electrical Networks
M. I. Fursanov
2010-01-01
Full Text Available The paper presents results of practical calculation for electric power technical losses on the basis of a combined calculation methodology for 0,38–10 kV electrical networks. The results have been evaluated and analyzed in the paper. The paper considers an influence of non-uniform loading of 0.38 kV network phases on electric power technical losses.
Сombined Calculation of Electric Power Technical Losses in 0,38–10 kV Electrical Networks
M. I. Fursanov; A. A. Zalatoi; V. V. Makarevich; A. I. Kuntsevich
2010-01-01
The paper presents results of practical calculation for electric power technical losses on the basis of a combined calculation methodology for 0,38–10 kV electrical networks. The results have been evaluated and analyzed in the paper. The paper considers an influence of non-uniform loading of 0.38 kV network phases on electric power technical losses.
D. Zalizny
2012-01-01
Full Text Available The paper proposes a real-time calculation algorithm of oil, winding and magnetic core temperature of power transformer on the basis of measured values of tank surface temperature and air temperature without measuring current. The algorithm is based on the calculation of the equivalent load factor of the transformer. Imitation simulation has confirmed efficiency of the algorithm. After tests on functioning transformers the algorithm can be used in thermal protection devices and diagnostic devices for power oil transformers.
TANG Yi; FANG Yong-li; YANG Luo; SUN Yu-xin; YU Zheng-hua
2012-01-01
A new accurate calculation method of electric power harmonic parameters was presented.Based on the delay time theorem of Fourier transform,the frequency of the electric power was calculated,and then,suing interpolation in the frequency domain of the windows,the parameters (amplitude and phase) of each harmonic frequency signals were calculated accurately.In the paper,the effect of the delay time and the windows on the electric power harmonic calculation accuracy was analysed.The digital simulation and the physical measurement tests show that the proposed method is effective and has more advantages than other methods which are based on multipoint interpolation especially in calculation time cost; therefore,it is very suitable to be used in the single chip DSP micro-processor.
Model calculating annual mean atmospheric dispersion factor for coastal site of nuclear power plant
无
2001-01-01
This paper describes an atmospheric dispersion field experiment performed on the coastal site of nuclear power plant in the east part of China during 1995 to 1996. The three-dimension joint frequency are obtained by hourly observation of wind and temperature on a 100m high tower; the frequency of the “event day of land and sea breezes” are given by observation of surface wind and land and sea breezes; the diffusion parameters are got from measurements of turbulent and wind tunnel simulation test.A new model calculating the annual mean atmospheric dispersion factor for coastal site of nuclear power plant is developed and established.This model considers not only the effect from mixing release and mixed layer but also the effect from the internal boundary layer and variation of diffusion parameters due to the distance from coast.The comparison between results obtained by the new model and current model shows that the ratio of annual mean atmospheric dispersion factor gained by the new model and the current one is about 2.0.
Xu Bao-Qing
2016-01-01
Full Text Available A simplified model of the 750kV tower is established by CDEGS software which is based on the Method Of Moment. The power frequency electric field distribution on the ground is achieved by software calculation and field-measuring. The validity of the calculation is proved when compare the calculation and experiment results. The model also can be used to calculate the electric field in prepared hanging points on the tower. Results show that the electric field distribution on the ground surface around the tower and prepared hanging points are meet the standard by calculation and experiment.
Anneé Miranda Carracedo
2012-12-01
Full Text Available Objetivo: personalizar las constantes A, factor cirujano y profundidad de la cámara anterior para las fórmulas de cálculo de la lente intraocular en la cirugía de catarata en el Instituto Cubano de Oftalmología "Ramón Pando Ferrer" de mayo de 2007 a enero de 2011. Métodos: se realizó un estudio descriptivo retrospectivo donde se estudiaron las constantes A, factor cirujano y profundidad de la cámara anterior. También se evaluó la longitud axial preoperatoria por IOL Master, la mejor agudeza visual sin corrección, el componente esférico esperado, el componente esférico obtenido y los resultados refractivos. Resultados: las constantes optimizadas por interferometría de coherencia parcial son diferentes a las propuestas por los fabricantes de las lentes intraoculares. Estas constantes personalizadas para cada cirujano no mostraron diferencias significativas. Las constantes optimizadas según las longitudes axiales, tienen diferencias significativas en los 3 grupos de estudio. La diferencia entre la lente intraocular implantada y la propuesta con las nuevas constantes resultó menor de 1 D de error en 83,1 % de los pacientes. El 75,4 % quedó bien corregido en relación con la diferencia entre la refracción esperada y la obtenida. Conclusiones: las constantes optimizadas por interferometría de coherencia parcial resultan más elevadas que las propuestas por el fabricante. La optimización de estas en el cálculo de la lente permite, de acuerdo a las características individuales de cada ojo (longitud axial, usar la fórmula adecuada e incrementa la predictibilidad de los resultados refractivos posoperatorios.Objective: to personalize the A, surgeon factor and anterior chamber depth constants for intraocular lens calculation formulas in the cataract surgery at the “Ramón Pando Ferrer” Cuban Ophthalmological Institute from May 2007 to January 2011. Method: a retrospective and descriptive study was made to study the A constant
Mayhall, D J; Stein, W; Gronberg, J B
2006-05-15
We have performed preliminary computer-based, transient, magnetostatic calculations of the eddy-current power loss in rotating titanium-alloy and aluminum wheels and wheel rims in the predominantly axially-directed, steady magnetic fields of two small, solenoidal coils. These calculations have been undertaken to assess the eddy-current power loss in various possible International Linear Collider (ILC) positron target wheels. They have also been done to validate the simulation code module against known results published in the literature. The commercially available software package used in these calculations is the Maxwell 3D, Version 10, Transient Module from the Ansoft Corporation.
Varsha M Rathi
2013-01-01
Full Text Available Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP lenses, soft and soft toric lenses, piggy back contact lenses (PBCL, hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL.
Yost, Dillon C.; Yao, Yi; Kanai, Yosuke
2017-09-01
In ion irradiation processes, electronic stopping power describes the energy transfer rate from the irradiating ion to the target material's electrons. Due to the scarcity and significant uncertainties in experimental electronic stopping power data for materials beyond simple solids, there has been growing interest in the use of first-principles theory for calculating electronic stopping power. In recent years, advances in high-performance computing have opened the door to fully first-principles nonequilibrium simulations based on real-time time-dependent density functional theory (RT-TDDFT). While it has been demonstrated that the RT-TDDFT approach is capable of predicting electronic stopping power for a wide range of condensed matter systems, there has yet to be an exhaustive examination of the physical and numerical approximations involved and their effects on the calculated stopping power. We discuss the results of such a study for crystalline silicon with protons as irradiating ions. We examine the influences of key approximations in RT-TDDFT nonequilibrium simulations on the calculated electronic stopping power, including approximations related to basis sets, finite size effects, exchange-correlation approximation, pseudopotentials, and more. Finally, we propose a simple and efficient correction scheme to account for the contribution from core-electron excitations to the stopping power, as it was found to be significant for large proton velocities.
TO THE CALCULATION OF THE ECONOMIC POTENTIAL OF WIND ENERGY AND THE CHOICE OF WIND POWER PLANTS
Vinnikov A. V.
2016-01-01
Full Text Available To determine the feasibility of using PV systems we should assess the economic efficiency of wind energy in the region. At the same time, the first step should be an analysis of upper-air and power characteristics of the wind. The next stage is to determine the energy source of wind power (theoretical, technical and economic potential. The basic approach to the calculation of economic indicators should include a determination of the effectiveness of wind power installations in competition with traditional energy sources in a particular region. There are important following indicators: the payback period and economic efficiency. If the economic potential of wind power satisfies the requirements, the next step is to study the technical requirements applicable to wind power stations. For a preliminary assessment of the terrain, the article discloses a sequence of events that must be performed to assess the effectiveness of the installation of wind power systems. We have listed advantages and disadvantages of the main types of wind power plants, and other ramifications of choosing of basic functional units. The considered in an article analytical expressions for calculating the evaluation of economic efficiency of wind energy, the technical requirements for the basic parameters of wind turbines and their main advantages, disadvantages and features the work will allow at the design stage to carry out a preliminary assessment of effectiveness of the wind power stations for a particular region and locality, specific types consumers in view of their modes of operation and the quality requirements of electricity
Stavenga, DG
2003-01-01
A wave-optical model for the integrated facet lens-rhabdomere system of fly eyes is used to calculate the effective light power in the rhabdomeres when the eye is illuminated with a point light source or with an extended source. Two rhabdomere types are considered: the slender rhabdomeres of R7,8 ph
Planar immersion lens with metasurfaces
Ho, John S; Tanabe, Yuji; Yeh, Alexander J; Fan, Shanhui; Poon, Ada S Y
2015-01-01
The solid immersion lens is a powerful optical tool that allows light entering material from air or vacuum to focus to a spot much smaller than the free-space wavelength. Conventionally, however, they rely on semispherical topographies and are non-planar and bulky, which limits their integration in many applications. Recently, there has been considerable interest in using planar structures, referred to as metasurfaces, to construct flat optical components for manipulating light in unusual ways. Here, we propose and demonstrate the concept of a planar immersion lens based on metasurfaces. The resulting planar device, when placed near an interface between air and dielectric material, can focus electromagnetic radiation incident from air to a spot in material smaller than the free-space wavelength. As an experimental demonstration, we fabricate an ultrathin and flexible microwave lens and further show that it achieves wireless energy transfer in material mimicking biological tissue.
Space Warps II. New Gravitational Lens Candidates from the CFHTLS Discovered through Citizen Science
More, Anupreeta; Marshall, Phil; More, Surhud; Baeten, Elisabeth; Wilcox, Julianne; Macmillan, Christine; Cornen, Claude; Kapadia, Amit; Parrish, Michael; Snyder, Chris; Davis, Chris; Gavazzi, Raphael; Lintott, Chris; Simpson, Robert; Miller, David; Smith, Arfon M; Paget, Edward; Saha, Prasenjit; Kueng, Rafael; Collett, Tom; Tecza, Matthias; Baumer, Michael
2015-01-01
We report the discovery of 28 promising and a total of 58 new lens candidates from the CFHT Legacy Survey (CFHTLS) based on about 11 million classifications performed by citizen scientists as part of the first Space Warps lens search. The goal of the blind lens search was to identify lenses missed by lens finding robots (the RingFinder on galaxy scales and ArcFinder on group/cluster scales), which have been previously used to mine the CFHTLS for lenses. We compare some properties of lens samples detected by these algorithms to the SpaceWarps sample and found that they are broadly similar. The image separation distribution calculated from the SpaceWarps discovered sample shows that our previous constraints on the average density profile of the lens population are robust. Space Warps recovers about 60% of the known sample and the new candidates show a richer variety compared to the lenses found by the two robots. We find that analyzing only those classifications which are performed by the high power volunteers,...
DISSECTING THE GRAVITATIONAL LENS B1608+656. I. LENS POTENTIAL RECONSTRUCTION
Suyu, S. H.; Marshall, P. J.; Blandford, R. D.; Fassnacht, C. D.; Koopmans, L. V. E.; McKean, J. P.; Treu, T.
2009-01-01
Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended source-intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential ( m
V. Shcherbich
2013-01-01
Full Text Available The paper presents information on elaboration of algorithms and programs for intra-station optimization of load distribution between power plants and calculation of equivalent energy characteristics the Berezovskaya GRES which is one of the components of the system for optimum load distribution between thermal power plants (TPP of the Belarusian power system. Description of the accepted technical concepts, algorithm and program structures, composition and methods for input-output data, organization of personnel work with programs of load optimization has been given in the paper.
Mirko Grljušić
2015-05-01
Full Text Available The aim of this research was to investigate the possibility of a combined heat & power (CHP plant, using the waste heat from a Suezmax-size oil tanker’s main engine, to meet all heating and electricity requirements during navigation. After considering various configurations, a standard propulsion engine operating at maximum efficiency, combined with a supercritical Organic Rankine cycle (ORC system, was selected to supply the auxiliary power, using R245fa or R123 as the working fluid. The system analysis showed that such a plant can meet all heat and electrical power requirements at full load, with the need to burn only a small amount of supplementary fuel in a heat recovery steam generator (HRSG when the main engine operates at part load. Therefore, it is possible to increase the overall thermal efficiency of the ship’s power plant by more than 5% when the main engine operates at 65% or more of its specified maximum continuous rating (SMCR.
Account of Consumer Power Sources in Calculations of Distributive Electrical Networks of 6–10 kV
M. I. Fursanov
2011-01-01
Full Text Available The methodical approach to calculation of normal modes of open 6–10 kV-electrical networks has been developed in the paper. These networks contain generating sources of consumers; they are equipped with means for automatic voltage control and they are operating in parallel with the power system.
Elsa Tavernier
Full Text Available We aimed to examine the extent to which inaccurate assumptions for nuisance parameters used to calculate sample size can affect the power of a randomized controlled trial (RCT. In a simulation study, we separately considered an RCT with continuous, dichotomous or time-to-event outcomes, with associated nuisance parameters of standard deviation, success rate in the control group and survival rate in the control group at some time point, respectively. For each type of outcome, we calculated a required sample size N for a hypothesized treatment effect, an assumed nuisance parameter and a nominal power of 80%. We then assumed a nuisance parameter associated with a relative error at the design stage. For each type of outcome, we randomly drew 10,000 relative errors of the associated nuisance parameter (from empirical distributions derived from a previously published review. Then, retro-fitting the sample size formula, we derived, for the pre-calculated sample size N, the real power of the RCT, taking into account the relative error for the nuisance parameter. In total, 23%, 0% and 18% of RCTs with continuous, binary and time-to-event outcomes, respectively, were underpowered (i.e., the real power was 90%. Even with proper calculation of sample size, a substantial number of trials are underpowered or overpowered because of imprecise knowledge of nuisance parameters. Such findings raise questions about how sample size for RCTs should be determined.
Hsu, Ming-Ying; Lin, Yu-Chuan; Chan, Chia-Yen; Lin, Wei-Cheng; Chan, Shenq-Tsong; Huang, Ting-Ming
2012-10-01
The Cassegrain telescope system in this study, is discussion correct lens thermal OPD (Optical Path Difference) effect optical performance. The correct lens assembly are includes several components such as correct lens, lens mount, spacer, mount barrel and retainer. The heat transfer from surrounding to the correct lens barrel will causes optical system aberration. Meanwhile, the off-axis rays path of the OPD must consider lens incidence point and emergence point. The correct lens temperature distribution is calculate the lens barrel heat transfer analysis, the thermal distortion and stress are solve by FEM (Finite Element Method) software. The temperature calculation results can be weighting to each incidence ray path and calculate thermal OPD. The thermal OPD on Z-direction can be fitted by rigid body motion and Zernike polynomial. The fitting results can be used to evaluate the thermal effect on correct lens assembly in telescope system.
Kovacević, M S; Nikezić, D
2006-09-10
A means of calculating optical power distribution in bent multimode optical fibers is proposed. It employs the power-flow equation approximated by the Fokker-Planck equation that is solved by the explicit finite-difference method. Conceptually important steps of this procedure include (i) dividing the full length of the bent optical fiber into a finite number of short, straight segments; (ii) solving the power equation for each segment sequentially to find its output distribution; and (iii) expressing that output distribution in rotated coordinates of the subsequent segment along the curved fiber to determine the input distribution for that subsequent segment and thus enable the calculation of the power flow and output distribution for it. The segment length and bend-induced perturbation of output angles are determined by geometric optics. The resulting power distributions are given at different cross sections along the curved fiber axis. They vary with the radius of fiber curvature and launch conditions. Results are compared to those for straight fiber. Bending loss is calculated as well.
Pirjola, R.
2008-07-01
"Geomagnetically induced currents" (GIC) in ground-based technological networks are a manifestation of space weather. GIC are a potential source of problems to the systems and therefore important in practice. GIC in a power system (or in principle in any other discretely-earthed system) can be calculated conveniently by using matrix equations presented earlier. Since temporal variations associated with GIC are slow compared to the 50/60 Hz frequency used in power transmission, a dc treatment is acceptable. An essential quantity in calculations of GIC in a power grid is the earthing impedance matrix, which is the transfer function coupling GIC flowing to (from) the Earth with the voltages between the earthing points, called nodes or (sub)stations, and a remote earth. The diagonal elements of the matrix equal the earthing resistances of the nodes whereas an off-diagonal element expresses how much GIC at one earthing point affects the voltage at another node. In GIC calculations, except for some special treatments of individual sites, the off-diagonal elements are usually neglected by saying simply that the earthing points (are assumed to) lie distantly enough. In this paper, we examine the effects of off-diagonal elements of the earthing impedance matrix, i.e. the effects of interactions between different stations, on GIC calculations in greater detail and more quantitatively than before. We consider a fictitious system that represents a high-voltage power grid and a simple "network" consisting of two stations with a line connecting them. For both systems, the conclusion can be drawn that the off-diagonal elements do not play a major role in practice. Modelling them only approximately, or even ignoring them, is not of great significance compared to other shortcomings involved in GIC calculations. This is particularly true when looking at a power grid as a whole although at some individual stations the neglect may lead to larger errors in GIC values.
Dellinger, T. C.; Hnat, J. G.; Marston, C. H.
1979-01-01
A parametric study of the performance of the MHD generator and combustor components of potential early commercial open-cycle MHD/steam power plants is presented. Consideration is given to the effects of air heater system concept, MHD combustor type, coal type, thermal input power, oxygen enrichment of the combustion, subsonic and supersonic generator flow and magnetic field strength on coupled generator and combustor performance. The best performance is found to be attained with a 3000 F, indirectly fired air heater, no oxygen enrichment, Illinois no. 6 coal, a two-stage cyclone combustor with 85% slag rejection, a subsonic generator, and a magnetic field configuration yielding a constant transverse electric field of 4 kV/m. Results indicate that optimum net MHD generator power is generally compressor-power-limited rather than electric-stress-limited, with optimum net power a relatively weak function of operating pressure.
R.V. Zaitsev
2016-09-01
Full Text Available Purpose. To ensure maximum production of electric power by photovoltaic vacilities, in addition to using highly efficient photovoltaic modules equipped with solar radiation concentrators must use a highly effective power take-off system. This paper is inscribed to solving the problem of a highly efficient and economic power take-off system development. Methodology. To solving the problem, we implemented three stages. On the first stage examines the dependence of electrical power from the intensity of the incident solar radiation. Based on this, the second stage is calculated the DC-DC converter resonant circuit and its working parameters, and developed circuit diagram of DC-DC converter. On the third stage, we carry out an analysis of power take-off system with step up DC-DC converter working. Results. In this paper, we carry out the analysis of working efficiency for photovoltaic facility power take-off system with step-up boost converter. The result of such analysis show that the efficiency of such system in a wide range of photovoltaic energy module illumination power is at 0.92, whereas the efficiency of classic power take-off systems does not exceed 0.70. Achieved results allow designing a circuit scheme of a controlled bridge resonant step-up converter with digital control. Proposed scheme will ensure reliable operation, fast and accurate location point of maximum power and conversion efficiency up to 0.96. Originality. Novelty of proposed power take-off system solution constitute in implementation of circuit with DC-DC converters, which as it shown by results of carrying out modeling is the most effective. Practical value. Practical implementation of proposed power take-off system design will allow reducing losses in connective wires and increasing the efficiency of such a system up to 92.5% in wide range of photovoltaic energy modules illumination.
Liquid lens using acoustic radiation force.
Koyama, Daisuke; Isago, Ryoichi; Nakamura, Kentaro
2011-03-01
A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.
叶向彧; 纪建丽; 张广斌; 王乐; 毛益辉; 何雪洪
2011-01-01
目的 精确的眼生物测量对人工晶状体(intraocular lens,IOL)度数计算至关重要,尤其是眼轴及角膜曲率的测量.本研究将对比新一代光学低相干反射生物测量仪Lenstar LS900 (Haag-Streit)与IOLMaster对眼前节参数及IOL测算的差异.方法 应用Lenstar LS900和IOLMaster分别对30例(60眼)老年性白内障患者进行眼轴长度、前房深度、角膜曲率和散光轴方面的测量比较;分别利用2种设备计算IOL度数,均选用SRK/T计算公式和SA60AT(Alcon)IOL,在确定同一度数的前提下比较目标屈光度的差异.结果 Lenstar LS900和IOLMaster测量眼轴长度、前房深度、平均角膜曲率、陡峭轴角膜曲率之间差异均无统计学意义(均为P＞0.05),且均具有良好的相关性(相关系数分别为0.999、0.955、0.936、0.845),而两种设备测得陡峭轴之间相关欠佳(r =0.579).Lenstar LS900和IOLMaster所获得的术后目标屈光度值分别为(-0.02±0.17)D和(-0.07±0.23)D,差异无统计学意义(P＞0.05).Bland-Altman分析显示,2种设备获得的目标屈光值具有良好的一致性.结论 Lenstar LS900和IOLMaster两种设备测量眼前节参数及IOL度数具有良好的一致性.同时,Lenstar LS900还可以快速、准确的为白内障患者和屈光医师提供更多的眼生物参数.%Objective To compare the difference of anterior segment biometry and intraocular lens (IOL) power measured by a new noncontact optical biometer Lenstar LS9O0 (Haag-Streit) using optical low-coherence reflectometry and IOLMaster. Methods Biometry measurements in 60 eyes of 30 patients scheduled for cataract surgery by the same examiner with Lenstar LS900 and IOLMaster, the axial length (AL) .anterior chamber depth (ACD) and keratometric (K) were compared,IOL power for AcrySof SA60AT( Alcon) measure by two devices using SRK/T formulas was calculated, and the difference of targeted diopter under same IOL power was compared. Results There was no statistical
李俊昌; 马琨; 樊则宾
2002-01-01
The vertical excitation axial-flux kilowatt CO2 laser is an equipment widely used in the high-power laser heat treatment industrial applications. The experimental measurements indicate that the power density distribution of laser beam is generally of ring distribution with a sunken at the center, therefore the laser beam cannot be simply regarded as base mode Gaussian beam. In this paper, such laser beam is regarded as the non-interference superposition of TEM00 and TEM01 mode beams, the method to determine the simulation parameters is discussed, and the relevant heat effect calculation equation is deduced.
The Impact of Harmonics Calculation Methods on Power Quality Assessment in Wind Farms
Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth
2010-01-01
Different methods of calculating harmonics in measurements obtained from offshore wind farms are shown in this paper. Appropriate data processing methods are suggested for harmonics with different origin and nature. Enhancements of discrete Fourier transform application in order to reduce...... measurement data processing errors are proposed and compared with classical methods. Comparison of signal processing methods for harmonic studies is presented and application dependent on harmonics origin and nature recommended. Certain aspects related to magnitude and phase calculation in stationary...... measurement data are analysed and described. Qualitative indices of measurement data harmonic analysis in order to assess the calculation accuracy are suggested and used....
Power calculation for comparing diagnostic accuracies in a multi-reader, multi-test design.
Kim, Eunhee; Zhang, Zheng; Wang, Youdan; Zeng, Donglin
2014-12-01
Receiver operating characteristic (ROC) analysis is widely used to evaluate the performance of diagnostic tests with continuous or ordinal responses. A popular study design for assessing the accuracy of diagnostic tests involves multiple readers interpreting multiple diagnostic test results, called the multi-reader, multi-test design. Although several different approaches to analyzing data from this design exist, few methods have discussed the sample size and power issues. In this article, we develop a power formula to compare the correlated areas under the ROC curves (AUC) in a multi-reader, multi-test design. We present a nonparametric approach to estimate and compare the correlated AUCs by extending DeLong et al.'s (1988, Biometrics 44, 837-845) approach. A power formula is derived based on the asymptotic distribution of the nonparametric AUCs. Simulation studies are conducted to demonstrate the performance of the proposed power formula and an example is provided to illustrate the proposed procedure.
An Augmented Virtuality Based Solar Energy Power Calculator in Electrical Engineering
Clement Ehimika Ohireime Onime
2015-02-01
Full Text Available It is becoming increasingly important to include information about power generation from renewable energy sources in the training of electrical engineers. Solar energy is arguably the most common renewable energy source in use today. Providing practical hands-on training on solar energy power generation today requires the use of photovoltaic panel devices which are used for transforming solar energy into electrical energy. In many developing countries, practical hands-on training on solar power generation is limited due to the cost of photovoltaic panel devices and so the training consists of theoretical and tutorial classes sometimes supported by remote and virtual laboratories. This paper presents an augmented virtuality tool where real-time information from a mobile device’s sensors is used directly within a virtual or computer generated environment. The tool provides a practical context for hands-on tutorial exercises on solar energy power generation.
Dinner, H. [KISSsoft AG, Hombrechtikon (Germany)
2007-07-01
KISSsys is a commercial software launched in the market three years ago. It is able to calculate power transmission in powertrains and combine this with strength calculations of the machine elements of the powertrain. This way, complete gearing/powertrain systems can be parametrized and analyzed with regard to strength and life. With KISSsys, users can make quick and detailed parameter studies of a complete gearing/powertrain system for an efficient comparison of design variants. KISSsys uses KISSsoft for strength and life calculations of the various machine elements. KISSsoft is a CAE software for fast and reliable design, optimisation and calculation of machine elements like toothed gears, shafts, bearings, bolts, shaft-hub joints and springs. KISSsoft is for users in transmission engineering and offers many optimisation possibilities. (orig.)
Mikulović Jovan Č.
2014-01-01
Full Text Available A methodology for calculation of overvoltages in transformer windings, based on a numerical method of inverse Laplace transform, is presented. Mathematical model of transformer windings is described by partial differential equations corresponding to distributed parameters electrical circuits. The procedure of calculating overvoltages is applied to windings having either isolated neutral point, or grounded neutral point, or neutral point grounded through impedance. A comparative analysis of the calculation results obtained by the proposed numerical method and by analytical method of calculation of overvoltages in transformer windings is presented. The results computed by the proposed method and measured voltage distributions, when a voltage surge is applied to a three-phase 30 kVA power transformer, are compared. [Projekat Ministartsva nauke Republike Srbije, br. TR-33037 i br. TR-33020
A New Sensorless MRAS Based on Active Power Calculations for Rotor Position Estimation of a DFIG
Gil Domingos Marques; Duarte Mesquita e Sousa
2011-01-01
A sensorless method for the estimation of the rotor position of the wound-rotor induction machine is described in this paper. The method is based on the MRAS methodology and consists in the comparison of two models for the evaluation of the active power transferred across the air gap: the reference model and the adaptive model. The reference model obtains the power transferred across the air gap using directly available and measured stator variables. The adaptive model obtains the same quanti...
Stubbs, David M.; Hsu, Ike C.
1991-12-01
This paper describes the optomechanical design, thermal analysis, fabrication, and test evaluation processes followed in developing a rapid cooled, infrared lens cell. Thermal analysis was the key engineering discipline exercised in the design phase. The effect of thermal stress on the lens, induced by rapid cooling of the lens cell, was investigated. Features of this lens cell that minimized the thermal stress will be discussed in a dedicated section. The results of thermal analysis on the selected lens cell design and the selection of the flow channel design in the heat exchanger will be discussed. Throughout the paper engineering drawings, illustrations, analytical results, and photographs of actual hardware are presented.
Jaffe, L. D.
1984-01-01
The CONC/11 computer program designed for calculating the performance of dish-type solar thermal collectors and power systems is discussed. This program is intended to aid the system or collector designer in evaluating the performance to be expected with possible design alternatives. From design or test data on the characteristics of the various subsystems, CONC/11 calculates the efficiencies of the collector and the overall power system as functions of the receiver temperature for a specified insolation. If desired, CONC/11 will also determine the receiver aperture and the receiver temperature that will provide the highest efficiencies at a given insolation. The program handles both simple and compound concentrators. The CONC/11 is written in Athena Extended FORTRAN (similar to FORTRAN 77) to operate primarily in an interactive mode on a Sperry 1100/81 computer. It could also be used on many small computers. A user's manual is also provided for this program.
Jaffe, L. D.
1984-02-15
CONC/11 is a computer program designed for calculating the performance of dish-type solar thermal collectors and power systems. It is intended to aid the system or collector designer in evaluating the performance to be expected with possible design alternatives. From design or test data on the characteristics of the various subsystems, CONC/11 calculates the efficiencies of the collector and the overall power system as functions of the receiver temperature for a specified insolation. If desired, CONC/11 will also determine the receiver aperture and the receiver temperature that will provide the highest efficiencies at a given insolation. The program handles both simple and compound concentrators. CONC/11 is written in Athena Extended Fortran (similar to Fortran 77) to operate primarily in an interactive mode on a Sperry 1100/81 computer. It could also be used on many small computers.
Exact calculation of power and sample size in bioequivalence studies using two one-sided tests.
Shen, Meiyu; Russek-Cohen, Estelle; Slud, Eric V
2015-01-01
The number of subjects in a pharmacokinetic two-period two-treatment crossover bioequivalence study is typically small, most often less than 60. The most common approach to testing for bioequivalence is the two one-sided tests procedure. No explicit mathematical formula for the power function in the context of the two one-sided tests procedure exists in the statistical literature, although the exact power based on Owen's special case of bivariate noncentral t-distribution has been tabulated and graphed. Several approximations have previously been published for the probability of rejection in the two one-sided tests procedure for crossover bioequivalence studies. These approximations and associated sample size formulas are reviewed in this article and compared for various parameter combinations with exact power formulas derived here, which are computed analytically as univariate integrals and which have been validated by Monte Carlo simulations. The exact formulas for power and sample size are shown to improve markedly in realistic parameter settings over the previous approximations.
Neumann, Christoph; Taub, Margaret A; Younkin, Samuel G; Beaty, Terri H; Ruczinski, Ingo; Schwender, Holger
2014-11-01
Case-parent trio studies considering genotype data from children affected by a disease and their parents are frequently used to detect single nucleotide polymorphisms (SNPs) associated with disease. The most popular statistical tests for this study design are transmission/disequilibrium tests (TDTs). Several types of these tests have been developed, for example, procedures based on alleles or genotypes. Therefore, it is of great interest to examine which of these tests have the highest statistical power to detect SNPs associated with disease. Comparisons of the allelic and the genotypic TDT for individual SNPs have so far been conducted based on simulation studies, since the test statistic of the genotypic TDT was determined numerically. Recently, however, it has been shown that this test statistic can be presented in closed form. In this article, we employ this analytic solution to derive equations for calculating the statistical power and the required sample size for different types of the genotypic TDT. The power of this test is then compared with the one of the corresponding score test assuming the same mode of inheritance as well as the allelic TDT based on a multiplicative mode of inheritance, which is equivalent to the score test assuming an additive mode of inheritance. This is, thus, the first time the power of these tests are compared based on equations, yielding instant results and omitting the need for time-consuming simulation studies. This comparison reveals that these tests have almost the same power, with the score test being slightly more powerful.
A physical approach of the short-term wind power prediction based on CFD pre-calculated flow fields
LI Li; LIU Yong-qian; YANG Yong-ping; HAN Shuang; WANG Yi-mei
2013-01-01
A physical approach of the wind power prediction based on the CFD pre-calculated flow fields is proposed in this paper.The flow fields are obtained based on a steady CFD model with the discrete inflow wind conditions as the boundary conditions,and a database is established containing the important parameters including the inflow wind conditions,the flow fields and the corresponding wind power for each wind turbine.The power is predicted via the database by taking the Numerical Weather Prediction (NWP)wind as the input data.In order to evaluate the approach,the short-term wind power prediction for an actual wind farm is conducted as an example during the period of the year 2010.Compared with the measured power,the predicted results enjoy a high accuracy with the annual Root Mean Square Error (RMSE) of 15.2％ and the annual MAE of 10.80％.A good performance is shown in predicting the wind power's changing trend.This approach is independent of the historical data and can be widely used for all kinds of wind farms including the newly-built wind farms.At the same time,it does not take much computation time while it captures the local air flows more precisely by the CFD model.So it is especially practical for engineering projects.
Nur Krisna, Dwita; Su'ud, Zaki
2017-01-01
Nuclear reactor technology is growing rapidly, especially in developing Nuclear Power Plant (NPP). The utilization of nuclear energy in power generation systems has been progressing phase of the first generation to the fourth generation. This final project paper discusses the analysis neutronic one-cooled fast reactor type Pb-Bi, which is capable of operating up to 20 years without refueling. This reactor uses Thorium Uranium Nitride as fuel and operating on power range 100-500MWtNPPs. The method of calculation used a computer simulation program utilizing the SRAC. SPINNOR reactor is designed with the geometry of hexagonal shaped terrace that radially divided into three regions, namely the outermost regions with highest percentage of fuel, the middle regions with medium percentage of fuel, and most in the area with the lowest percentage. SPINNOR fast reactor operated for 20 years with variations in the percentage of Uranium-233 by 7%, 7.75%, and 8.5%. The neutronic calculation and analysis show that the design can be optimized in a fast reactor for thermal power output SPINNOR 300MWt with a fuel fraction 60% and variations of Uranium-233 enrichment of 7%-8.5%.
Ohga, Yukiharu; Fukuda, Mitsuko; Shibata, Kiyotaka; Kawakami, Takashi; Matsuzaki, Tomokazu
2005-01-01
A system has been developed to improve the efficiency of maintenance work while decreasing the radiation exposure of maintenance personnel in nuclear power plants. The input data for dose rate calculation are automatically generated by using computer-aided design data. Changes for the input data corresponding to the progress of maintenance work, such as installation of a radiation shield and removal of a component, are easily input interactively on a graphical user interface (GUI). A new method was proposed which searches the sets of source and detector points between which gamma-ray attenuation is changed by the component movement. The calculation is performed only for the changed sets, so that the change of the three-dimensional dose rate distribution is calculated rapidly according to the work progress. The dose rate distribution and the radiation exposure of maintenance personnel are displayed three-dimensionally in colour with plant components and pipes on the GUI.
Finch Stephen J
2005-04-01
Full Text Available Abstract Background Phenotype error causes reduction in power to detect genetic association. We present a quantification of phenotype error, also known as diagnostic error, on power and sample size calculations for case-control genetic association studies between a marker locus and a disease phenotype. We consider the classic Pearson chi-square test for independence as our test of genetic association. To determine asymptotic power analytically, we compute the distribution's non-centrality parameter, which is a function of the case and control sample sizes, genotype frequencies, disease prevalence, and phenotype misclassification probabilities. We derive the non-centrality parameter in the presence of phenotype errors and equivalent formulas for misclassification cost (the percentage increase in minimum sample size needed to maintain constant asymptotic power at a fixed significance level for each percentage increase in a given misclassification parameter. We use a linear Taylor Series approximation for the cost of phenotype misclassification to determine lower bounds for the relative costs of misclassifying a true affected (respectively, unaffected as a control (respectively, case. Power is verified by computer simulation. Results Our major findings are that: (i the median absolute difference between analytic power with our method and simulation power was 0.001 and the absolute difference was no larger than 0.011; (ii as the disease prevalence approaches 0, the cost of misclassifying a unaffected as a case becomes infinitely large while the cost of misclassifying an affected as a control approaches 0. Conclusion Our work enables researchers to specifically quantify power loss and minimum sample size requirements in the presence of phenotype errors, thereby allowing for more realistic study design. For most diseases of current interest, verifying that cases are correctly classified is of paramount importance.
2012-08-01
gearbox with pneumatic shift actuator. The differential connects to the final drives at the front axle. There are wheel end reduction units (WERU) at...regenerative braking or simulated engine braking . AVL Hybrid Control System (HCU) coordinates and controls all system components as laid out in Figure...HMMWV for the current given inputs based on the current vehicle speed, acceleration pedal, and brake pedal. From this driver requested power at the
Characteristic calculation of directional coupler for accelerator high-power feeders
Egorov, M A; Kaminsky, V I; Sobenin, N P; Zavadtsev, A A
2001-01-01
The calculation results of directional couplers with connection via the waveguide common narrow wall a coupling factor of 3.0 decibels,directivity no less than 20 decibels,adjustment of coupling factor at +- 1 decibels are presented. The adjustment is carried out with the help of cylindrical plungers, moving inside of waveguides on the part of broad walls in the location of the connection slot,and prismatic plungers,moving in rectangular waveguides connected to narrow walls opposite to a slot of connection. The device as a magic tee with movable throttle pistons in E- and H-plane arms permitting to match any load is designed too. The calculations are executed for devices operating at frequencies of 2.797 and 1.3 GHz.
Intraocular lens with accommodation capacity
Dorronsoro, Carlos; Alejandre, Nicolás; Bekesi, Nandor; Marcos, Susana
2014-01-01
Intraocular lens with accommodation capacity comprising a first optical member (1) having a dynamic optical power, to which a second optical member (2) with a fixed optical power is affixed, in such a manner that at least a central part of each of one of one of the curved surfaces (2a, 2b) of the second optical member (2) and of at least one of the surfaces (1a, 1b) of the first optical member (1) are in contact with each other, the second optical member (2) and the first optical member (1) p...
A New Sensorless MRAS Based on Active Power Calculations for Rotor Position Estimation of a DFIG
Gil Domingos Marques
2011-01-01
Full Text Available A sensorless method for the estimation of the rotor position of the wound-rotor induction machine is described in this paper. The method is based on the MRAS methodology and consists in the comparison of two models for the evaluation of the active power transferred across the air gap: the reference model and the adaptive model. The reference model obtains the power transferred across the air gap using directly available and measured stator variables. The adaptive model obtains the same quantity in function of electromotive forces and rotor currents that are measurable on the rotor position, which is under estimation. The method does not need any information about the stator or rotor flux and can be implemented in the rotor or in the stator reference frames with a hysteresis or with a PI controller. The stability analysis gives an unstable region on the rotor current dq plane. Simulation and experimental results show that the method is appropriate for the vector control of the doubly fed induction machine under the stability region.
Variable-focus cylindrical liquid lens array
Zhao, Wu-xiang; Liang, Dong; Zhang, Jie; Liu, Chao; Zang, Shang-fei; Wang, Qiong-hua
2013-06-01
A variable-focus cylindrical liquid lens array based on two transparent liquids of different refractive index is demonstrated. An elastic membrane divides a transparent reservoir into two chambers. The two chambers are filled with liquid 1 and liquid 2, respectively, which are of different refractive index. The micro-clapboards help liquid 1, liquid 2 and the elastic membrane form a cylindrical lens array. Driving these two liquids to flow can change the shape of the elastic membrane as well as the focal length. In this design, the gravity effect of liquid can be overcome. A demo lens array of positive optical power is developed and tested. Moreover, a potential application of the proposed lens array for autostereoscopic 3D displays is emphasized.
Outcomes of Sutureless Iris-Claw Lens Implantation
Nowomiejska, Katarzyna; Moneta-Wielgoś, Joanna; Jünemann, Anselm G. M.
2016-01-01
Purpose. To evaluate the indications, refraction, and visual and safety outcomes of iris-claw intraocular lens implanted retropupillary with sutureless technique during primary or secondary operation. Methods. Retrospective study of case series. The Haigis formula was used to calculate intraocular lens power. In all cases the wound was closed without suturing. Results. The study comprised 47 eyes. The mean follow-up time was 15.9 months (SD 12.2). The mean preoperative CDVA was 0.25 (SD 0.21). The final mean CDVA was 0.46 (SD 0.27). No hypotony or need for wound suturing was observed postoperatively. Mean postoperative refractive error was −0.27 Dsph (−3.87 Dsph to +2.85 Dsph; median 0.0, SD 1.28). The mean postoperative astigmatism was −1.82 Dcyl (min −0.25, max −5.5; median −1.25, SD 1.07). Postoperative complications were observed in 10 eyes. The most common complication was ovalization of the iris, which was observed in 8 eyes. The mean operation time was 35.9 min (min 11 min, max 79 min; median 34, SD 15.4). Conclusion. Retropupilary iris-claw intraocular lens (IOL) implantation with sutureless wound closing is an easy and fast method, ensuring good refractive outcome and a low risk of complication. The Haigis formula proved to be predictable in postoperative refraction. PMID:27642519
Varsha M Rathi; Preeji S Mandathara; Srikanth Dumpati
2013-01-01
Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the En...
Ümit Kamış
2012-12-01
Full Text Available During intraocular surgery, undesired damages of various etiology may occur in adjacent tissues. One of these tissues is the crystalline lens, which may be traumatized both in anterior segment and posterior segment surgeries, and when damaged, it usually causes marked decrease in visual acuity. The leading causes of iatrogenic lens injuries are intravitreal injection, laser iridotomy, phakic intraocular lens implantation, anterior chamber paracentesis, and vitreoretinal surgery. When crystalline lens damage occurs, its negative effect on visual function may be eliminated by performing cataract surgery intraoperatively or in elective conditions. (Turk J Ophthalmol 2012; 42: Supplement 27-30
In vivo Comet assay--statistical analysis and power calculations of mice testicular cells.
Hansen, Merete Kjær; Sharma, Anoop Kumar; Dybdahl, Marianne; Boberg, Julie; Kulahci, Murat
2014-11-01
The in vivo Comet assay is a sensitive method for evaluating DNA damage. A recurrent concern is how to analyze the data appropriately and efficiently. A popular approach is to summarize the raw data into a summary statistic prior to the statistical analysis. However, consensus on which summary statistic to use has yet to be reached. Another important consideration concerns the assessment of proper sample sizes in the design of Comet assay studies. This study aims to identify a statistic suitably summarizing the % tail DNA of mice testicular samples in Comet assay studies. A second aim is to provide curves for this statistic outlining the number of animals and gels to use. The current study was based on 11 compounds administered via oral gavage in three doses to male mice: CAS no. 110-26-9, CAS no. 512-56-1, CAS no. 111873-33-7, CAS no. 79-94-7, CAS no. 115-96-8, CAS no. 598-55-0, CAS no. 636-97-5, CAS no. 85-28-9, CAS no. 13674-87-8, CAS no. 43100-38-5 and CAS no. 60965-26-6. Testicular cells were examined using the alkaline version of the Comet assay and the DNA damage was quantified as % tail DNA using a fully automatic scoring system. From the raw data 23 summary statistics were examined. A linear mixed-effects model was fitted to the summarized data and the estimated variance components were used to generate power curves as a function of sample size. The statistic that most appropriately summarized the within-sample distributions was the median of the log-transformed data, as it most consistently conformed to the assumptions of the statistical model. Power curves for 1.5-, 2-, and 2.5-fold changes of the highest dose group compared to the control group when 50 and 100 cells were scored per gel are provided to aid in the design of future Comet assay studies on testicular cells.
Improving accuracy of the calculation of in-core power distributions for light water reactors
Tsuiki, M.; Beere, W.H. (Institute for energy technology, OECD Halden Reactor Project (Norway))
2009-10-15
Comparisons have been made of VNEM prototype system to the measured data obtained from Ringhals unit 3 NPP at its beginning of life, hot-stand-by state. Three cases with difference control rod bank positions and Boron concentrations have been compared: Case 1: nearly all rod banks withdrawn, Boron = 1315 ppm Case 2: bank C = nearly half-inserted, bank D = fully inserted, Boron = 1131 ppm Case 3: banks C and D = fully inserted, Boron = 1060 ppm The results can be summarized as: error: maximum detector reading (%) error: keff (%) Case 1 -2.1 -0.175 Case 2 1.5 -0.022 Case 3 -0.5 -0.044 Excellent agreement was observed in the comparison of the neutron detector readings and the core eigenvalues. The method of core modelling and parameters used in calculation of VNEM is completely the same as the 'PWR standard option' determined from similar comparisons of VNEM and other PWRs. No empirical, or any sort of adjustment was done. (author)
Mechanical Calculation of Power Lines and Strands in Overhead Transmission Lines
Li Yongping
2016-01-01
Full Text Available This paper discusses the issue of shape and stress of overhead transmission lines. It fully considers that the conductor is subjected to axial force, shear, bending moment simultaneousiy. And the flat wire is basically in the elastic range. Because the stress is the strength of a certain point, the bending rigidity of the overhead lines can not be ignored. However, the catenary has been used in previous research and the force of the overhead lines is obtained on this basis. The author establishes a model of wire calculation under real condition, and gives a feasible simplified model. And then it gives the line shape formula, internal force formula, formula of stress in the strands. The results show that the original stress is significantly smaller.In this paper, the stress formula is almost close to the reality. It proves the reliability of the simplified model that the line shape includes the original flexible part.The results can not only fill the gaps in the theoretical study of the overhead lines, but also have some guidance to the production and design of overhead lines.
Zahra Nasrazadani
2017-02-01
Full Text Available The heavy water zero power reactor (HWZPR, which is a critical assembly with a maximum power of 100 W, can be used in different lattice pitches. The last change of core configuration was from a lattice pitch of 18–20 cm. Based on regulations, prior to the first operation of the reactor, a new core was simulated with MCNP (Monte Carlo N-Particle-4C and WIMS (Winfrith Improved Multigroup Scheme–CITATON codes. To investigate the criticality of this core, the effective multiplication factor (Keff versus heavy water level, and the critical water level were calculated. Then, for safety considerations, the reactivity worth of D2O, the reactivity worth of safety and control rods, and temperature reactivity coefficients for the fuel and the moderator, were calculated. The results show that the relevant criteria in the safety analysis report were satisfied in the new core. Therefore, with the permission of the reactor safety committee, the first criticality operation was conducted, and important physical parameters were measured experimentally. The results were compared with the corresponding values in the original core.
Superlensing Microscope Objective Lens
Yan, Bing; Parker, Alan; Lai, Yukun; Thomas, John; Yue, Liyang; Monks, James
2016-01-01
Conventional microscope objective lenses are diffraction limited, which means that they cannot resolve features smaller than half the illumination wavelength. Under white light illumination, such resolution limit is about 250-300 nm for an ordinary microscope. In this paper, we demonstrate a new superlensing objective lens which has a resolution of about 100 nm, offering at least two times resolution improvement over conventional objectives in resolution. This is achieved by integrating a conventional microscope objective lens with a superlensing microsphere lens using a 3D printed lens adaptor. The new objective lens was used for label-free super-resolution imaging of 100 nm-sized engineering and biological samples, including a Blu-ray disc sample, semiconductor chip and adenoviruses. Our work creates a solid base for developing a commercially-viable superlens prototype, which has potential to transform the field of optical microscopy and imaging.
Effects of Coupling Lens on Optical Refrigeration of Semiconductors
DING Kai; ZENG Yi-Ping
2008-01-01
Optical refrigeration of semiconductors is encountering efficiency difficulties caused by nonradiative recombination and luminescence trapping.A commonly used approach for enhancing luminescence efficiency of a semiconductor device is coupling a lens with the device. We quantitatively study the effects of a coupling lens on optical refrigeration based on rate equations and photon recycling,and calculated cooling efficiencies of different coupling mechanisms and of different lens materials.A GaAs/GaInP heterostructure coupled with a homo-epitaxial GaInP hemispherical lens is recommended.
RegPT: Direct and fast calculation of regularized cosmological power spectrum at two-loop order
Taruya, Atsushi; Nishimichi, Takahiro; Codis, Sandrine
2012-01-01
We present a specific prescription for the calculation of cosmological power spectra, exploited here at two-loop order in perturbation theory (PT), based on the multi-point propagator expansion. In this approach power spectra are constructed from the regularized expressions of the propagators that reproduce both the resummed behavior in the high-k limit and the standard PT results at low-k. With the help of N-body simulations, we show that such a construction gives robust and accurate predictions for both the density power spectrum and the correlation function at percent-level in the weakly non-linear regime. We then present an algorithm that allows accelerated evaluations of all the required diagrams by reducing the computational tasks to one-dimensional integrals. This is achieved by means of pre-computed kernel sets defined for appropriately chosen fiducial models. The computational time for two-loop results is then reduced from a few minutes, with the direct method, to a few seconds with the fast one. The...
Pink-beam focusing with a one-dimensional compound refractive lens.
Dufresne, Eric M; Dunford, Robert W; Kanter, Elliot P; Gao, Yuan; Moon, Seoksu; Walko, Donald A; Zhang, Xusheng
2016-09-01
The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm(-2) was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental. Only the fundamental of the undulator focuses at the experiment. A two-chopper system reduces the power density on the imaging system and lens by four orders of magnitude, enabling imaging of the focal plane without any X-ray filter. A method to measure such high power density as well as the performance of the lens in focusing the pink beam is reported.
Curved plasma channels: Kerr lens and Airy prism
Kasparian, Jérôme; 10.2971/jeos.2009.09039
2010-01-01
We analytically calculate the transverse energy fluxes that would be respectively induced in high-power Airy beams by the Kerr self-focusing and the Airy profile itself if they were the only active process. In experimental condition representative of laser filamentation experiments of high-power ultrashort laser pulses in air and condensed media, the Kerr lens induces transverse energy fluxes much larger than the Airy "prism" at the main peak. As a consequence, the curved plasma channels in Airy beams are not only a plasma spark on a curved focus, but indeed self-guided filaments, and their curved trajectory appears as a perturbation due to the linear Airy propagation regime.
21 CFR 886.1430 - Ophthalmic contact lens radius measuring device.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic contact lens radius measuring device... lens radius measuring device. (a) Identification. An ophthalmic contact lens radius measuring device is an AC-powered device that is a microscope and dial gauge intended to measure the radius of a...
Atom lens without chromatic aberrations
Efremov, Maxim A; Schleich, Wolfgang P
2012-01-01
We propose a lens for atoms with reduced chromatic aberrations and calculate its focal length and spot size. In our scheme a two-level atom interacts with a near-resonant standing light wave formed by two running waves of slightly different wave vectors, and a far-detuned running wave propagating perpendicular to the standing wave. We show that within the Raman-Nath approximation and for an adiabatically slow atom-light interaction, the phase acquired by the atom is independent of the incident atomic velocity.
Kostal, M.; Juricek, V.; Rypar, V.; Svadlenkova, M. [Research Center Rez Ltd., 250 68 Husinec-Rez 130 (Czech Republic); Cvachovec, F. [Univ. of Defence, Kounicova 65, 662 10 Brno (Czech Republic)
2011-07-01
The power density distribution in a reactor has significant influence on core structures and pressure vessel mechanical resistance, as well as on the physical characteristics of nuclear fuel. This quantity also has an effect on the leakage neutron and photon field. This issue has become of increasing importance, as it touches on actual questions of the VVER nuclear power plant life time extension. This paper shows the comparison of calculated and experimentally determined pin by pin power distributions. The calculation has been performed with deterministic and Monte Carlo approaches. This quantity is accompanied by the neutron and photon flux density calculation and measurements at different points of the light water zero-power (LR-0) research reactor mock-up core, reactor built-in component (core barrel), and reactor pressure vessel and model. The effect of the different data libraries used for calculation is discussed. (authors)
Unitary lens semiconductor device
Lear, Kevin L.
1997-01-01
A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.
Salazar, M.A.; Foreman, L.R.
1997-07-08
This invention describes a method for fabricating an intraocular lens made from clear Teflon{trademark}, Mylar{trademark}, or other thermoplastic material having a thickness of about 0.025 millimeters. These plastic materials are thermoformable and biocompatable with the human eye. The two shaped lenses are bonded together with a variety of procedures which may include thermosetting and solvent based adhesives, laser and impulse welding, and ultrasonic bonding. The fill tube, which is used to inject a refractive filling material is formed with the lens so as not to damage the lens shape. A hypodermic tube may be included inside the fill tube. 13 figs.
Salazar, Mike A. (Albuquerque, NM); Foreman, Larry R. (Los Alamos, NM)
1997-01-01
This invention describes a method for fabricating an intraocular lens made rom clear Teflon.TM., Mylar.TM., or other thermoplastic material having a thickness of about 0.025 millimeters. These plastic materials are thermoformable and biocompatable with the human eye. The two shaped lenses are bonded together with a variety of procedures which may include thermosetting and solvent based adhesives, laser and impulse welding, and ultrasonic bonding. The fill tube, which is used to inject a refractive filling material is formed with the lens so as not to damage the lens shape. A hypodermic tube may be included inside the fill tube.
N. J. Milardovich
2014-10-01
Full Text Available A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially-available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.
Yoshida, Yutaka; Yokoyama, Kiyoko; Ishii, Naohiro
Many reports show that dominant frequency of high frequency component(HF:0.15∼0.4Hz) of heart rate time series is synchronized with the respiratory frequency. In this paper, we proposed the method for estimating the condition of respiration continuously using dominant frequency and power of HF (HFP) of heart rate time series. Dominant frequency and HFP is calculated from the interval of the neighboring two extreme points and the subtraction of the neighboring two extremals.In the experimental results, high frequency components did not disappear completely during breath-holding. This fact is different from the previous study. Subjects were classified into two groups. In one group, dominant frequency of the HF is significant increased during breath-holding compared with normal breathing. In the other group, this phenomenon was not observed. On the other hand, HFP of total subjects significantly decreased during breath-holding compared with normal breathing. Correct rate during breath-holding and error rate during rest and recovery are calculated using HFP. In the results, average and S. D. of correct rate during breath-holding were 65.0±26.3%. Correct rate of 18 subjects was 80.0±14.1% and correct rate of other 8 subjects was 31.5±11.9%. Our method is expected to apply to the development of the respiratory monitor which can measure respiratory condition with non-restricted in continuously.
Full Text Available ... Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent Oct ... easy answer, and neither one considers long-term impacts. Phakic Intraocular Lenses for Nearsightedness FEB 27, 2017 ...
Full Text Available ... lenses without a prescription in the United States. All contact lenses are medical devices that require a ... no such thing as a "one size fits all" contact lens. Lenses that are not properly fitted ...
Full Text Available ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her with a corneal abrasion. ... Studies Look at Effects of Marijuana on Vision FEB ...
Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her ...
Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms ...
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Full Text Available ... Vision and Daily Eye Drops After One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume Contacts May Contain Chemicals ...
Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... 2016 More Eye Health News Studies Look at Effects of Marijuana on Vision FEB 28, 2017 By ...
Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ...
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Full Text Available ... glow-in-the-dark lizard lenses, costume contacts can certainly add a spooky, eye-popping touch. But ... consideration as a standard contact lens because they can be purchased over-the-counter or on the ...
Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...
Full Text Available ... Healthy Contact Lens Use May 31, 2016 Is El Niño Making Your Allergies Worse? May 16, 2016 ... Number: * Email: * Enter code: * Message: Thank you Your feedback has been sent.
Wang, Yun; Lan, Tian; Ni, Guoqiang
2016-12-20
We propose a scheme for designing a new optical receiving system that can reduce the received-energy spot size via integration of a compound parabolic concentrator with a hemispherical lens. SolidWorks is used to model the receiving system, while TracePro is employed for simulations. The field of view is set to 30° and the radius of the compound parabolic concentrator outlet is 5 mm, which is also the radius of the hemispherical lens. Ray-tracing results show that under the given simulation conditions, the radius of the spot area is reduced from 5 to 3 mm at the receiving system and the gain is 5.2. In regard to the relations between received power and the radius of the hemispherical lens R, and the received power and the distance d between the compound parabolic concentrator and hemispherical lens, our detailed analysis yields the following characteristics: (1) the received power increases as R increases, but decreases as d increases; (2) as R increases, the spot area increases and the received flux is dispersed over the receiving plane, which dispersion is disadvantageous for high-speed communication; (3) the gain of the receiving system also varies with R and d; (4) an increase in d leads to decrease in the received flux and gain when d>-2 mm. Based on these characteristics, we set R=5 mm and calculate the energy efficiency. We obtain maximum energy efficiencies for different detection areas.
Novel fabrication technique of hybrid structure lens array for 3D images
Lee, Junsik; Kim, Junoh; Kim, Cheoljoong; Shin, Dooseub; Koo, Gyohyun; Won, Yong Hyub
2016-03-01
Tunable liquid lens arrays can produce three dimensional images by using electrowetting principle that alters surface tensions by applying voltage. This method has advantages of fast response time and low power consumption. However, it is challenging to fabricate a high fill factor liquid lens array and operate three dimensional images which demand high diopter. This study describes a hybrid structure lens array which has not only a liquid lens array but a solid lens array. A concave-shape lens array is unavoidable when using only the liquid lens array and some voltages are needed to make the lens flat. By placing the solid lens array on the liquid lens array, initial diopter can be positive. To fabricate the hybrid structure lens array, a conventional lithographic process in semiconductor manufacturing is needed. A negative photoresist SU-8 was used as chamber master molds. PDMS and UV adhesive replica molding are done sequentially. Two immiscible liquids, DI water and dodecane, are injected in the fabricated chamber, followed by sealing. The fabricated structure has a 20 by 20 pattern of cylindrical shaped circle array and the aperture size of each lens is 1mm. The thickness of the overall hybrid structure is about 2.8mm. Hybrid structure lens array has many advantages. Solid lens array has almost 100% fill factor and allow high efficiency. Diopter can be increased by more than 200 and negative diopter can be shifted to the positive region. This experiment showed several properties of the hybrid structure and demonstrated its superiority.
Eismann, Ulrich
2015-01-01
In their article, the authors of [Opt. Express 23, 4981 (2015)] observe step-like behavior and hysteresis of the output power of a diode-end-pumped Nd:YVO 4-laser as a function of pump power. While claiming that this behavior is a proof of thermal lensing in the intra-cavity TGG, no direct evidence is given. We will discuss here the validity of their statement, and propose an experimental proof.
罗保根; 张济明; 李龙标
2012-01-01
Objective To compare the derived intraocular astigmatism axis using power vector analysis method with the toric intraocular lens (TIOL) axis by slitlamp observation after cataract phacoemulsification. Methods A cohort of 39 patients (41 eyes) who had cataract phacoemulsification with Alcon AcrySof(R) toric lens implantation were studied 3 months postoperatively.Postoperative refraction and keratometric cylinder were recorded.Internal astigmatism and axes was obtained using power vector analysis method to assess the TIOL axes.The intraocular astigmatism axis and the TIOL axis observed by slitlamp were compared by linear relationship.Uncorrected distance visual acuities (UDVA) and corrected distance visual acuities (CDVA) were also measured. Results Postoperatively,the eyes had UDVA better than that of preoperatively (P ＜0.05).The difference between the 2 methods of assessing IOL axis was 4.64 ± 3.06 degrees (range 0 to 14.33 degrees).The correlation was significant (r =0.997,P ＜0.01). Conclusions Power vector analysis method is a suitable method for assessing toric IOL alignment.%目的 比较AcrySot(R)散光人工晶状体植入术后眼内散光轴向和裂隙灯观察散光人工晶状体的标记轴向的差别.方法 对39例41只眼超声乳化白内障吸除联合AcrySof(R)散光人工晶状体植入术患者,术后三个月进行远视力及屈光状态测定,用散光矢量分析方法计算得眼内散光轴向与用裂隙灯观察的散光人工晶状体的标记轴向进行直线相关分析.结果 超声乳化白内障术后裸眼视力较术前提高(P＜0.05),眼内散光轴向与散光人工晶状体的标记轴向呈直线相关(r=0.997,P＜0.01).结论 散光矢量分析方法可以用于超声乳化术后散光人工晶状体轴向位置测定.
Fundamentals of concentric lens systems synthesis
Ezhova, Kseniia; Zverev, Victor; Tochilina, Tatiana; Tymoshchuk, Irina
2016-09-01
Introduction of coefficients defining the relationship of the radii of curvature of the surfaces of concentric optical systems, allowed the transformation of the obtained analytical relations in a system of two equations with two unknowns. It is shown that the existence of the solution of the system of equations determined by the optical constants of the selected lens material. The results of the analysis of the conditions of the chromatic aberration correction position and the sequence of obtaining of the system equations define the theoretical basis of the engineering method of parametric synthesis of concentric lens systems. Application of the developed method is illustrated by examples of calculation particular systems design build.
The Frontier Fields Lens Modeling Comparison Project
Meneghetti, M; Coe, D; Contini, E; De Lucia, G; Giocoli, C; Acebron, A; Borgani, S; Bradac, M; Diego, J M; Hoag, A; Ishigaki, M; Johnson, T L; Jullo, E; Kawamata, R; Lam, D; Limousin, M; Liesenborgs, J; Oguri, M; Sebesta, K; Sharon, K; Williams, L L R; Zitrin, A
2016-01-01
Gravitational lensing by clusters of galaxies offers a powerful probe of their structure and mass distribution. Deriving a lens magnification map for a galaxy cluster is a classic inversion problem and many methods have been developed over the past two decades to solve it. Several research groups have developed techniques independently to map the predominantly dark matter distribution in cluster lenses. While these methods have all provided remarkably high precision mass maps, particularly with exquisite imaging data from the Hubble Space Telescope (HST), the reconstructions themselves have never been directly compared. In this paper, we report the results of comparing various independent lens modeling techniques employed by individual research groups in the community. Here we present for the first time a detailed and robust comparison of methodologies for fidelity, accuracy and precision. For this collaborative exercise, the lens modeling community was provided simulated cluster images -- of two clusters Are...
Xu, Dandan; Schneider, Peter; Springel, Volker; Vogelsberger, Mark; Nelson, Dylan; Hernquist, Lars
2015-01-01
The combination of dynamical and strong gravitational lensing studies of massive galaxies shows that their total density profile in the central region (i.e. up to a few half-light radius) can be described by a power law, $\\rho(r)\\propto r^{-\\gamma}$. Therefore, such a power-law model is employed for a large number of strong-lensing applications, including the so-called time-delay technique used to infer the Hubble constant $H_0$. However, since the radial scale at which strong lensing features are formed (i.e., the Einstein radius) corresponds to the transition from the dominance of baryonic matter to dark matter, there is no known reason why galaxies should follow a power law in density. The assumption of a power law artificially breaks the mass-sheet degeneracy, a well-known invariance transformation in gravitational lensing which affects the product of Hubble constant and time delay and can therefore cause a bias in the determination of $H_0$ from the time-delay technique. In this paper, we use the Illustr...
A single-pixel wireless contact lens display
Lingley, A. R.; Ali, M.; Liao, Y.; Mirjalili, R.; Klonner, M.; Sopanen, M.; Suihkonen, S.; Shen, T.; Otis, B. P.; Lipsanen, H.; Parviz, B. A.
2011-12-01
We present the design, construction and in vivo rabbit testing of a wirelessly powered contact lens display. The display consists of an antenna, a 500 × 500 µm2 silicon power harvesting and radio integrated circuit, metal interconnects, insulation layers and a 750 × 750 µm2 transparent sapphire chip containing a custom-designed micro-light emitting diode with peak emission at 475 nm, all integrated onto a contact lens. The display can be powered wirelessly from ~1 m in free space and ~2 cm in vivo on a rabbit. The display was tested on live, anesthetized rabbits with no observed adverse effect. In order to extend display capabilities, design and fabrication of micro-Fresnel lenses on a contact lens are presented to move toward a multipixel display that can be worn in the form of a contact lens. Contact lenses with integrated micro-Fresnel lenses were also tested on live rabbits and showed no adverse effect.
Anbaraki, Afrooz; Khoshaman, Kazem; Ghasemi, Younes; Yousefi, Reza
2016-10-01
The main components of sunlight reaching the eye lens are UVA and visible light exerting their photo-damaging effects indirectly by the aid of endogenous photosensitizer molecules such as riboflavin (RF). In this study, lens proteins solutions were incubated with RF and exposed to the sunlight. Then, gel mobility shift analysis and different spectroscopic assessments were applied to examine the structural damaging effects of solar radiation on these proteins. Exposure of lens proteins to direct sunlight, in the presence of RF, leads to marked structural crosslinking, oligomerization and proteolytic instability. These structural damages were also accompanied with reduction in the emission fluorescence of Trp and Tyr and appearance of a new absorption peak between 300 and 400nm which can be related to formation of new chromophores. Also, photo-oxidation of lens crystallins increases their oligomeric size distribution as examined by dynamic light scattering analysis. The above mentioned structural insults, as potential sources of sunlight-induced senile cataract and blindness, were significantly attenuated in the presence of ascorbic acid and glutathione which are two important components of lens antioxidant defense system. Therefore, the powerful antioxidant defense mechanism of eye lens is an important barrier against molecular photo-damaging effects of solar radiations during the life span. Copyright © 2016 Elsevier B.V. All rights reserved.
The mechanical response of the porcine lens to a spinning test.
Reilly, Matthew A; Martius, Philipp; Kumar, Saurav; Burd, Harvey J; Stachs, Oliver
2016-06-01
The pig lens has been used as a model for presbyopia as pigs lack accommodative ability. Previous studies using microindentation have indicated that the shear modulus distribution is qualitatively similar to that of the aged human lens and that the lens does not alter its refractive power due to equatorial stretching. A lens spinning test was used to determine whether prior lens stiffness data obtained from a sectioned porcine lens were reliable and whether the testing conditions significantly influence the lens' mechanical properties. The elastic modulus distribution determined for fresh lenses closely matched that measured previously using a microindentation test. Confocal scanning laser microscopy was used to evaluate changes to the lens' structure arising from mechanical stress and following storage for up to one week.
Frequency Invariant Beam Steering for Short-Pulse Systems with a Rotman Lens
Andreas Lambrecht
2010-01-01
Full Text Available A promising approach for beam steering of high-voltage transient signals for HPEM-systems (High Power Electro Magnetic is presented. The inherent capability of the Rotman lens to provide true time delays is used to develop a prototype beam steering device for an antielectronics HPEM system in the frequency range from 350 MHz to 5 GHz. Results of analytical calculations, simulations, and measurements from a hardware prototype are presented. The detailed mechanical setup of the Rotman lens is presented. Additionally the output pulses are investigated when inputting a Gaussian-like transient signal. Then time domain measures of quality (full width at half maximum, ringing, delay spread, maximum of transfer function are investigated for these output transients, and the simulation and measurement results are compared. A concluding analysis of the realizable time domain array pattern shows the radiated pulse form.
Minus Piggyback Lens Overlaying ReSTOR® Multifocal Lens in High Myopia
Isha Gupta
2013-06-01
Full Text Available Background: We report the case of a 40-year-old female patient treated with implantation of the Acrysof® IQ ReSTOR® lens (Alcon, Fort Worth, Tex., USA with overlaying Acrysof EXpand® minus piggyback lens (Alcon. Methods: The patient had high myopia and was diagnosed with presbyopia and bilateral posterior subcapsular cataract. She desired to be spectacle-free and opted to undergo bilateral placement of the ReSTOR multifocal lens. The necessary intraocular lens (IOL power was +3.5 in the right eye and +4.0 in the left eye, though the range of commercially available ReSTOR lenses is +6.0 to +34.0 D. In order to achieve emmetropia in this case of high myopia, it was determined that an EXpand minus piggyback lens would be necessary. Results: Implantation of the ReSTOR lens with overlaying EXpand minus piggyback lens was performed successfully and without complication. At 5 months postoperatively, the patient had 20/20 uncorrected visual acuity in both eyes. She reported a high level of satisfaction and was able to return to her daily activities including reading and driving without spectacles. Conclusion: We report successful primary implantation of AcrySof EXpand minus piggyback lenses overlying the AcrySof IQ ReSTOR lens in a patient with high myopia. Long-term follow-up and further evaluation is necessary to establish piggyback IOL implantation with multifocal IOL as an accepted treatment for high myopia with presbyopia.
Proskuryakov, K.N. (Moskovskij Ehnergeticheskij Inst. (USSR))
1983-03-01
Mathematical models are proposed for calculating acoustic oscillation resonance frequencies in the coolant in various components of the WWER type primary circuit (core, steam generator, pressurizer, piping). Due to the correspondence between model calculations and experimental results obtained in operating nuclear power plants, the developed models can be used for practical calculations. The possibility of calculating the eigenfrequencies of the coolant oscillation under different operating conditions leads to the interpretation of operational data, to the analysis of operational conditions, to the detection of coolant boiling in the reactor, and to design changes in order to prevent resonance oscillations within the coolant.
Goluoglu, S.
2001-01-11
Transportation of low-enriched uranium (LEU) and mixed-oxide (MOX) assemblies to and within the VVER-1000-type Balakovo Nuclear Power Plant is investigated. Effective multiplication factors for fresh fuel assemblies on the railroad platform, fresh fuel assemblies in the fuel transportation vehicle, and fresh fuel assemblies in the spent fuel storage pool are calculated. If there is no absorber between the units, the configurations with all MOX assemblies result in higher effective multiplication factors than the configurations with all LEU assemblies when the system is dry. When the system is flooded, the configurations with all LEU assemblies result in higher effective multiplication factors. For normal operating conditions, effective multiplication factors for all configurations are below the presumed upper subcritical limit of 0.95. For an accident condition of a fully loaded fuel transportation vehicle that is flooded with low-density water (possibly from a fire suppression system), the presumed upper subcritical limit is exceeded by configurations containing LEU assemblies.
A guide for calculation of spot size to determine power density for free fiber irradiation of tissue
Tate, Lloyd P., Jr.; Blikslager, Anthony T.
2005-04-01
Transendoscopic laser treatment for upper airway disorders has been performed in the horse for over twenty years. Endoscopic laser transmission utilizing flexible fiber optics is limited to certain discreet wavelengths. Initially, the laser of choice was the Nd: YAG laser (1064nm), but in the early 1990's, diode lasers (810nm, 980nm) were introduced to veterinary medicine and are currently used in private practice and universities. Precise application of laser irradiation is dependent on the user knowing the laser's output as well as the amount of energy that is delivered to tissue. Knowledge of dosimetry is important to the veterinarian for keeping accurate medical records by being able to describe very specific treatment regimes. The applied energy is best described as power density or energy density. Calculation of this energy is dependent upon the users ability to determine the laser's spot size when irradiating tissue in a non-contact mode. The charts derived from this study provide the veterinarian the ability to estimate spot size for a number of commonly used lasers with the fiber positioned at various distances from the target.
Inaniwa, T.; Kanematsu, N.
2016-10-01
The stopping power ratio (SPR) of body tissues relative to water depends on the particle energy. For simplicity, however, most analytical dose planning systems do not account for SPR variation with particle energy along the beam’s path, but rather assume a constant energy for SPR estimation. The range error due to this simplification could be indispensable depending on the particle species and the assumed energy. This error can be minimized by assuming a suitable energy referred to as an ‘effective energy’ in SPR estimation. To date, however, the effective energy has never been investigated for realistic patient geometries. We investigated the effective energies for proton, helium-, carbon-, and oxygen-ion radiotherapy using volumetric models of the reference male and female phantoms provided by the International Commission on Radiological Protection (ICRP). The range errors were estimated by comparing the particle ranges calculated when particle energy variations were and were not considered. The effective energies per nucleon for protons and helium, carbon, and oxygen ions were 70 MeV, 70 MeV, 131 MeV, and 156 MeV, respectively. Using the determined effective energies, the range errors were reduced to ⩽0.3 mm for respective particle species. For SPR estimation of multiple particle species, an effective energy of 100 MeV is recommended, with which the range error is ⩽0.5 mm for all particle species.
Refinery Power Load Calculation and Transformer Selection%炼油厂电力负荷计算及变压器选型
张红启
2015-01-01
Starting from the "calculation method for electricity load design in petroleum refineries" (SH/T 3116-2000) standard, the calculation method of axial power was introduced as well as the derivation process of shaft power formula, the computational load of other power equipments was calculated by the demand coefficient method, the maximum load on the device was calculated as well as the capacity of reactive power compensation. Considering the transformer active power loss and reactive power loss, the design and selection of the transformer were verified.%从《炼油厂用电负荷设计计算方法》（SH/T 3116-2000）标准入手，介绍了轴功率的计算方法及轴功率公式的推导过程，采用需要系数法计算了其它电力设备的计算负荷，对装置的最大计算负荷及无功功率补偿容量进行了计算，在考虑变压器有功功率损耗及无功功率损耗后，对变压器的设计选型进行验证。
Preliminary of Optical Lens Design for Micro-Satellite
Rachim, Elvira; Mukhtar Tahir, Andi; Herawan, Agus
2017-01-01
The development of micro satellites for the last two decades is emerging rapidly as the need of satellite communication usage is increasing. Earth observation is one of the example of how satellites are on demand. Most observation satellites consist of sensors and imaging system on-board. One of the key element to have a good imaging system is a special optical lens system design. Such lens is designed specifically by calculating every parameter such as refractive, reflective indexes, type of surface, distance and many more. Manufactured lenses sometimes do not match the requirement of an imager system hence the special lens design is needed. This paper will first briefly describe the history of optic, theory related to lens system, then the design and the analysis of lens system for micro-satellites generally and LAPAN A4 particularly.
PSAT 在电力系统潮流计算教学中的应用%Application of PSAT simulation software in teaching of power flow calculation
周晓华; 王荔芳; 刘胜永
2016-01-01
将 PSAT 仿真技术应用于电力系统分析课程计算机潮流计算的教学中，通过电力系统的潮流计算实例，介绍了利用 PSAT 软件建模、参数设置及仿真分析的过程.PSAT 仿真得到的计算结果与 Matpower 仿真计算结果基本一致.应用 PSAT 软件可使电力系统潮流计算的原理与概念形象化，将原理性内容更直观地展示出来，有利于加深学生对基本理论的理解，提高电力系统分析课程的教学效果.%In order to improve the teaching effect of the course of Power System Analysis, the PSAT simulation technology can be applied to the teaching of power flow calculation using computer in Power System Analysis course.This paper introduces the software modeling,analysis,parameter settings and simulation process by using the case of power flow calculation. The calculation results obtained by simulation experiments are in accordance with the calculation results of Matpower simulation software.The application of PSAT software makes the principles or concepts of power flow calculation visualized and displays the original rational content more intuitive.The flexible use of simulation teaching plays a vital role for enhancing the students’learning interest,deepening students’understanding of the basic theory of power flow calculation.
Cubic optical elements for an accommodative intraocular lens.
Simonov, Aleksey N; Vdovin, Gleb; Rombach, Michiel C
2006-08-21
We present a new accommodative intraocular lens based on a two-element varifocal Alvarez lens. The intraocular lens consists of (1) an anterior element combining a spherical lens for refractive power with a cubic surface for the varifocal effect, and (2) a posterior element with a cubic surface only. The focal length of the IOL lens changes when the superimposed refractive elements shift in opposite directions in a plane perpendicular to the optical axis. The ciliary muscle will drive the accommodation by a natural process of contraction and relaxation. Results of ray-tracing simulations of the model eye with the two-element intraocular lens are presented for on-axis and off-axis vision. The configuration of the lens is optimized to reduce refractive errors as well as effects of misalignment. A prototype with a clear aperture of ~5.7 mm is manufactured and evaluated in air with a Shack-Hartmann wave-front sensor. It provides an accommodation range of ~4 dioptres in the eye at a ~0.75-mm lateral displacement of the optical elements. The experimentally measured on-axis optical performance of the IOL lens agrees with the theoretically predicted performance.
TU-E-201-03: Eye Lens Dosimetry in Radiotherapy Using Contact Lens-Shaped Applicator
Park, J. [Seoul National University Hospital (Korea, Republic of)
2015-06-15
. These actions should be considered when they are consistent with the clinical task and patient anatomy. Learning Objectives: To become familiar with method of eye dose estimation for patient in specific situation of brain perfusion CT To become familiar with level of eye lens radiation doses in patients undergoing brain perfusion MDCT To understand methods for reducing eye lens dose to patient Jong Min Park, Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea Eye lens dosimetry in radiotherapy using contact lens-shaped applicator Dose calculation accuracy of commercial treatment planning systems is relatively low at shallow depths. Therefore, in-vivo measurements are often performed in the clinic to verify delivered doses to eye lens which are located at shallow depth. Current in-vivo dosimetry for eye lens during radiotherapy is generally performed with small in-vivo dosimeters on the surface of patient eyelid. Since this procedure potentially contains considerable uncertainty, a contact lens-shaped applicator made of acrylic (lens applicator) was developed for in-vivo measurements of eye lens dose during radiotherapy to reduce uncertainty. The lens applicator allows the insertion of commercially available metal oxide semiconductor field effect transistor (MOSFET) dosimeters. Computed tomography (CT) images of an anthropomorphic phantom with and without the lens applicator were acquired. A total of 20 VMAT plans were delivered to an anthropomorphic phantom and the doses with the lens applicator and the doses at the surface of the eyelid were measured using both micro and standard MOSFET dosimeters. The differences in measured dose at the surface of the eyelid from the calculated lens dose were acquired. The differences between the measured and the calculated doses at the lens applicator, as well as the differences between the measured and the calculated doses at the surface of the eyelid were acquired. The statistical significance of the
TU-E-201-01: Methods for Eye Lens Dosimetry and Studies On Lens Opacities with Interventionists
Rehani, M. [Massachusetts General Hospital (United States)
2015-06-15
. These actions should be considered when they are consistent with the clinical task and patient anatomy. Learning Objectives: To become familiar with method of eye dose estimation for patient in specific situation of brain perfusion CT To become familiar with level of eye lens radiation doses in patients undergoing brain perfusion MDCT To understand methods for reducing eye lens dose to patient Jong Min Park, Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea Eye lens dosimetry in radiotherapy using contact lens-shaped applicator Dose calculation accuracy of commercial treatment planning systems is relatively low at shallow depths. Therefore, in-vivo measurements are often performed in the clinic to verify delivered doses to eye lens which are located at shallow depth. Current in-vivo dosimetry for eye lens during radiotherapy is generally performed with small in-vivo dosimeters on the surface of patient eyelid. Since this procedure potentially contains considerable uncertainty, a contact lens-shaped applicator made of acrylic (lens applicator) was developed for in-vivo measurements of eye lens dose during radiotherapy to reduce uncertainty. The lens applicator allows the insertion of commercially available metal oxide semiconductor field effect transistor (MOSFET) dosimeters. Computed tomography (CT) images of an anthropomorphic phantom with and without the lens applicator were acquired. A total of 20 VMAT plans were delivered to an anthropomorphic phantom and the doses with the lens applicator and the doses at the surface of the eyelid were measured using both micro and standard MOSFET dosimeters. The differences in measured dose at the surface of the eyelid from the calculated lens dose were acquired. The differences between the measured and the calculated doses at the lens applicator, as well as the differences between the measured and the calculated doses at the surface of the eyelid were acquired. The statistical significance of the
Dating the time of birth: a radiocarbon calibration curve for human eye lens crystallines
Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen
2010-01-01
Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth......, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy...
Compari son and Analysis of Several Calculations of Power System Flow%几种电力系统潮流计算的比较与分析
姚勇; 李健; 王雨虹
2013-01-01
Power system power flow calculation is one of the research on power grid planning and operation analysis method, it plays a decisive role in the power system. The purpose of this paper is to use C language and write Newton-Raphson method rectangular coordinate method, Newton-Raphson method-polar coordinate method, P-Q decomposition method and Gauss-Seidel method of power flow calculation program according to the principle of power flow calculation. Then, compare with different trend programs, including check instance USES the IEEE standard example, this paper analyzed their respective applicable occasions and superiority.%电力系统潮流计算是对电力网规划、运行研究分析的一种方法，其在电力系统中具有举足轻重的作用。本文旨在利用C语言根据潮流计算原理编写出牛顿---拉夫逊直角坐标法、牛顿拉夫逊---极坐标法、P-Q分解法以及高斯-赛德尔法的潮流计算程序，然后对不同潮流程序进行比较，其中校验实例采用IEEE标准算例，分析出它们各自的适用场合及优越性。
New trends in intraocular lens imaging
Millán, María S.; Alba-Bueno, Francisco; Vega, Fidel
2011-08-01
As a result of modern technological advances, cataract surgery can be seen as not only a rehabilitative operation, but a customized procedure to compensate for important sources of image degradation in the visual system of a patient, such as defocus and some aberrations. With the development of new materials, instruments and surgical techniques in ophthalmology, great progress has been achieved in the imaging capability of a pseudophakic eye implanted with an intraocular lens (IOL). From the very beginning, optical design has played an essential role in this progress. New IOL designs need, on the one hand, theoretical eye models able to predict optical imaging performance and on the other hand, testing methods, verification through in vitro and in vivo measurements, and clinical validation. The implant of an IOL requires a precise biometry of the eye, a prior calculation from physiological data, and an accurate position inside the eye. Otherwise, the effects of IOL calculation errors or misplacements degrade the image very quickly. The incorporation of wavefront aberrometry into clinical ophthalmology practice has motivated new designs of IOLs to compensate for high order aberrations in some extent. Thus, for instance, IOLs with an aspheric design have the potential to improve optical performance and contrast sensitivity by reducing the positive spherical aberration of human cornea. Monofocal IOLs cause a complete loss of accommodation that requires further correction for either distance or near vision. Multifocal IOLs address this limitation using the principle of simultaneous vision. Some multifocal IOLs include a diffractive zone that covers the aperture in part or totally. Reduced image contrast and undesired visual phenomena, such as halos and glare, have been associated to the performance of multifocal IOLs. Based on a different principle, accommodating IOLs rely on the effort of the ciliary body to increase the effective power of the optical system of the
Gatland, Ian R.
2002-01-01
Proposes a ray tracing approach to thin lens analysis based on a vector form of Snell's law for paraxial rays as an alternative to the usual approach in introductory physics courses. The ray tracing approach accommodates skew rays and thus provides a complete analysis. (Author/KHR)
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Research of the long-focus Maksutov telephoto lens
Tarasov, I. P.; Tsyganok, E. A.
2016-04-01
The article presents the research result and the optical design of long-focus telephoto lens for photo shooting by the academician Maksutov's scheme. It shows a review of lenses for photo shooting on the market today, and also an analysis of the correctional possibilities which is based on the scheme is presented; studied long-focus telephoto lens is compared with its closest analog, the calculation of a new telephoto lens with higher image quality is made on the basis of that comparison.
An Atomic Lens Using a Focusing Hollow Beam
夏勇; 印建平; 王育竹
2003-01-01
We propose a new method to generate a focused hollow laser beam by using an azimuthally distributed 2π-phase plate and a convergent thin lens, and calculate the intensity distribution of the focused hollow beam in free propagation space. The relationship between the waist w0 of the incident collimated Gaussian beam and the dark spot size of the focused hollow beam at the focal point, and the relationship between the focal length f of the thin lens and the dark spot size are studied respectively. The optical potential of the blue-detuned focused hollow beam for 85Rb atoms is calculated. Our study shows that when the larger waist w of the incident Gaussian beam and the shorter focal length f of the lens are chosen, we can obtain an extremely small dark spot size of the focused hollow beam, which can be used to form an atomic lens with a resolution of several angstroms.
Fernandez, Juan C.; Bisceglia, Mateo; Acosta, Eduardo O. [Universidad de Buenos Aires (Argentina). Facultad de Ingenieria. Lab. de Electrooptica]. E-mail: jcfernan@fi.uba.ar
2001-07-01
The used methods for calculation of produced electromagnetic fields by power transmission lines, assumes straight power transmission lines working in parallel to a plane soil. The influence of the associated curvature to its weight is depreciated, or it is introduced by means of a horizontal line of a intermediate height among the maximum and minimum heights of the power line. In this work it is compared the created values by horizontal and catenary lines. By means of investigations, it has been found a situation where for larger arrows there are great differences between the exact calculation and the approximation of horizontal line, and also the situation which shows that the better approximation is obtained by means of placing the horizontal line something above the minimum height.
基于Matlab的某轻型货车动力性计算%Power Performance Calculation of Light Truck Based on Matlab
吴心平; 郏国中; 贾振华
2011-01-01
结合教学实际,利用Matlab的强大数学计算功能和绘图功能,开发出了汽车动力性计算程序,并对某轻型货车进行了动力性计算。该程序应用于教学实际,改变了传统教学模式,激发了学生学习兴趣,提高了教学效果。%Starting from teaching practice,using the powerful function of math and drawing of Matlab,this paper introduces the computer calculation program of power performance,and calculates the power performance of light truck.It is intended to be applied in the p
Shchinnikov, P. A.; Safronov, A. V.
2014-12-01
General principles of a procedure for matching energy balances of thermal power plants (TPPs), whose use enhances the accuracy of information-measuring systems (IMSs) during calculations of performance characteristics (PCs), are stated. To do this, there is the possibility for changing values of measured and calculated variables within intervals determined by measurement errors and regulations. An example of matching energy balances of the thermal power plants with a T-180 turbine is made. The proposed procedure allows one to reduce the divergence of balance equations by 3-4 times. It is shown also that the equipment operation mode affects the profit deficiency. Dependences for the divergence of energy balances on the deviation of input parameters and calculated data for the fuel economy before and after matching energy balances are represented.
运用PowerShell计算行×列表X2检验%To Calculate Contingency Table chi-square Test by PowerShell
王正凯
2008-01-01
微软已经推出功能强大的PowerShell 1.0,并决定在未来的新操作系统中内置PowerShell,PowerShell本身具有完善的数学计算和多维数组功能,只需通过简单脚本编程就可以方便地计算医学统计中经常遇到的行×列表X2检验问题.
Diaz, Daniel Suescun
2007-07-01
This work presents two new methods for the solution of the inverse point kinetics equation. The first method is based on the integration by parts of the integral of the inverse point kinetics equation, which results in a power series in terms of the nuclear power in time dependence. Applying some conditions to the nuclear power, the reactivity is represented as first and second derivatives of this nuclear power. This new calculation method for reactivity has special characteristics, amongst which the possibility of using different sampling periods, and the possibility of restarting the calculation, after its interruption associated it with a possible equipment malfunction, allowing the calculation of reactivity in a non-continuous way. Apart from this reactivity can be obtained with or without dependency on the nuclear power memory. The second method is based on the Laplace transform of the point kinetics equations, resulting in an expression equivalent to the inverse kinetics equation as a function of the power history. The reactivity can be written in terms of the summation of convolution with response to impulse, characteristic of a linear system. For its digital form the Z-transform is used, which is the discrete version of the Laplace transform. In this method it can be pointed out that the linear part is equivalent to a filter named Finite Impulse Response (Fir). The Fir filter will always be, stable and non-varying in time, and, apart from this, it can be implemented in the non-recursive way. This type of implementation does not require feedback, allowing the calculation of reactivity in a continuous way. The proposed methods were validated using signals with random noise and showing the relationship between the reactivity difference and the degree of the random noise. (author)
Braun, Mathias [Lippstadt (Germany)
2010-07-15
This paper presents a resume of the practical experiences for use in technical calculations. The author intends to avoid that the trainee professionals be oriented to the extensive of the tables, dispensing the electrotechnical fundamentals. The calculation is step by step developed and followed by conceptual explanation. This article will be published into two parts, being this part the first one to be presented.
O.V. Golik
2013-09-01
Full Text Available Results of cable transmitting capacity calculation for voltage of up to 220 kV are analyzed. The work is devoted to creation of a current rating calculation technique for high-voltage cross-linked polyethylene cables.
Hordósy Gábor
2016-01-01
Full Text Available A major project was launched at Paks NPP, Hungary, to investigate the possibility of lifetime extension up to 60 years. At the same time, new fuel types with higher enrichment and containing pins with gadolinium have been introduced. Due to these plans, the radiation load of the pressure vessel was evaluated up to 60 years irradiation, taking into account the past and planned future cycles. The computational procedure, elaborated and validated earlier for the fast flux calculation in the pressure vessel was modified for the new fuel types. The neutron source at the core boundaries was taken from core design calculations and the neutron transport from the source to and through the pressure vessel was followed by Monte Carlo calculations. A number of calculations were performed to adequately follow the change of the neutron source. The paper details this procedure, the used Monte Carlo model, the influence of the different reloading schemes on the radiation load and the calculated results.
Hordósy, Gábor; Hegyi, György; Keresztúri, András; Maráczy, Csaba; Temesvári, Emese; Zsolnay, Éva M.
2016-02-01
A major project was launched at Paks NPP, Hungary, to investigate the possibility of lifetime extension up to 60 years. At the same time, new fuel types with higher enrichment and containing pins with gadolinium have been introduced. Due to these plans, the radiation load of the pressure vessel was evaluated up to 60 years irradiation, taking into account the past and planned future cycles. The computational procedure, elaborated and validated earlier for the fast flux calculation in the pressure vessel was modified for the new fuel types. The neutron source at the core boundaries was taken from core design calculations and the neutron transport from the source to and through the pressure vessel was followed by Monte Carlo calculations. A number of calculations were performed to adequately follow the change of the neutron source. The paper details this procedure, the used Monte Carlo model, the influence of the different reloading schemes on the radiation load and the calculated results.
Gradient-index ophthalmic lens design and polymer material studies
Fischer, David Joel
Unifocal ophthalmic lenses are conventionally designed using homogeneous glass or plastic materials and aspheric surfaces. The desired power and aberration correction are provided by selection of surface shape and refractive index. This thesis studies the design of ophthalmic lenses utilizing gradient-index (GRIN) materials for both the optical power and aberration control. This is done using geometrical optical theory and ray-tracing simulations. Progressive addition lenses (PALS) are vision correction lenses with a continuous change in power used to treat presbyopia. The power variation is typically located in the lower half of the lens. Progressive addition lenses are currently made with aspheric surfaces to achieve the focal power transition and aberration control. These surfaces have at most, mirror symmetry about the vertical axis. The possible design of progressive addition lenses with GRIN materials has not been well studied. This thesis studies PALS and identifies how gradient-index materials can be used to provide both the power progression and aberration control. The optical theory for rotationally symmetric and asymmetric power additions is given. Analytical and numerical methods for calculating the index profile are used, and the results examined using ray-tracing simulations. The theory developed for ophthalmic lenses is applied to the design of GRIN axicon. This is the first GRIN axicon manufactured, and is fabricated using ion-exchanged GRIN glass. Experimental measurements of its performance are compared and found to match theoretical predictions. This demonstrates the generality of the theory developed: it may be applied to non-visual applications, and even to non-imaging applications. Realistic implementation of GRIN technology to ophthalmic application requires the fabrication of large scale refractive index gradients in polymer material systems. The methyl-methacrylate/styrene copolymer system is studied to develop an empirical model of its
MALDI-MS-imaging of whole human lens capsule.
Ronci, Maurizio; Sharma, Shiwani; Chataway, Tim; Burdon, Kathryn P; Martin, Sarah; Craig, Jamie E; Voelcker, Nicolas H
2011-08-05
The ocular lens capsule is a smooth, transparent basement membrane that encapsulates the lens and is composed of a rigid network of interacting structural proteins and glycosaminoglycans. During cataract surgery, the anterior lens capsule is routinely removed in the form of a circular disk. We considered that the excised capsule could be easily prepared for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging (MALDI-MSI) analysis. MALDI-MSI is a powerful tool to elucidate the spatial distribution of small molecules, peptides, and proteins within tissues. Here, we apply this molecular imaging technique to analyze the freshly excised human lens capsule en face. We demonstrate that novel information about the distribution of proteins by MALDI-MSI can be obtained from this highly compact connective tissue, having no evident histo-morphological characteristics. Trypsin digestion carried out on-tissue is shown to improve MALDI-MSI analysis of human lens capsules and affords high repeatability. Most importantly, MALDI-MSI analysis reveals a concentric distribution pattern of proteins such as apolipoprotein E (ApoE) and collagen IV alpha-1 on the anterior surface of surgically removed lens capsule, which may indicate direct or indirect effects of environmental and mechanical stresses on the human ocular lens.
Alipchenkov, V. M.; Belikov, V. V.; Davydov, A. V.; Emel'yanov, D. A.; Mosunova, N. A.
2013-05-01
Closing relations describing friction pressure drop during the motion of two-phase flows that are widely applied in thermal-hydraulic codes and in calculations of the parameters characterizing the flow of water coolant in the loops of reactor installations used at nuclear power stations and in other thermal power systems are reviewed. A new formula developed by the authors of this paper is proposed. The above-mentioned relations are implemented in the HYDRA-IBRAE thermal-hydraulic computation code developed at the Nuclear Safety Institute of the Russian Academy of Sciences. A series of verification calculations is carried out for a wide range of pressures, flowrates, and heat fluxes typical for transient and emergency operating conditions of nuclear power stations equipped with VVER reactors. Advantages and shortcomings of different closing relations are revealed, and recommendations for using them in carrying out thermal-hydraulic calculations of coolant flow in the loops of VVER-based nuclear power stations are given.
Tan, Zhenyu; Liu, Wei
2013-12-01
Systematic calculations are performed for determining the stopping powers (SP) and inelastic mean free paths (IMFP) for 20 eV-20 keV electrons in 11 types of human tissue. The calculations are based on a dielectric model, including the Born-Ochkur exchange correction. The optical energy loss functions (OELF) are empirically evaluated, because of the lack of available experimental optical data for the 11 tissues under consideration. The evaluated OELFs are examined by the f-sum rule expected from the dielectric response theory, and by calculation of the mean excitation energy. The calculated SPs are compared with those for PMMA (polymethylmethacrylate, a tissue equivalent material) and liquid water. The SP and IMFP data presented here are the results for the 11 human tissues over the energy range of 20 eV-20 keV, and are of importance in radiotherapy planning and for studies of various radiation effects on human tissues.
Rajaee, Meraj; Ghorashi, Seyed Mohamad Bagher
2015-08-01
Concentrator photovoltaic modules are a promising technology for highly efficient solar energy conversion. This system presents several advantages due to additional degrees of freedom that has been provided by the spectral separation such as cost and mass reduction, increase in the incident solar flux on PV cells and performances. This paper has proposed a unique photovoltaic solar cell system that consists of semi-Fresnel lens convergent structure and a novel two axis sun tracking module to enhance the efficiency of solar cell by using less cell area and energy losses. The grooves of this lens are calculated according to the refraction and convergent angles of the light easy for perpendicular incidence angle. The update time interval during tracking causes misalignment of the lens' optical axis versus the sunrays. Then an inventive sun-tracking method is introduced to adjust the module so that the incident rays are always perpendicular to the module's surface. As a result, all rays will be refracted with the predetermined angles. This way the focus area is reduced and smaller cells can be used. We also mentioned different module connections in order to provide compensation method during losses, for networks and power systems. Experimental results show that using semi-Fresnel lens, along with the sun-tracking method increases the efficiency of PV panel.
Shinano, Yuji; Yoshihara, Toshiyuki; Miyashiro, Ryuhei; Fukagawa, Youzou
The present paper considers optimization of lens adjustment in semiconductor lithography equipment. For improving productivity, the laser irradiation power of recent semiconductor lithography equipment has been boosted, which causes significant aberration due to heating during exposure. The aberration of the equipment must be measured or estimated in order to adjust the positions and orientations of the lenses. Since this adjustment is performed sequentially during exposure, the optimization problem to obtain optimal lens adjustment should be solved within a time as short as 100 ms. Although the problem of calculating the optimal lens adjustment can be naturally formulated as a convex minimization problem, in such a formulation the objective function is convex but includes several nondifferentiable points. Hence, optimization methods based on derivatives cannot be applied. Other approaches using derivative-free optimization or meta-heuristic methods cannot guarantee that the obtained solutions are truly optimal. Therefore, we formulate the optimization problem as quadratically constrained and second-order cone programming problems, which can be handled by solvers using an interior point method. Using the proposed formulations, computational experiments demonstrate that the optimal lens adjustment is obtained in a practical computational time, which is much less than 100 ms.
Polarization aberrations of radiation at the lens focus
Sokolov, AL
2005-01-01
The polarization aberrations of radiation at the lens focus are calculated with allowance for diffraction effects. Calculations are performed using the representation of radiation as a coherent set of Hermite-Gauss modes with certain amplitudes, phases, and polarizations. An expression for the longi
Rietveld, Cornelius A.; Johannesson, Magnus; Magnusson, Patrik K. E.; Uitterlinden, André G.; van Rooij, Frank J. A.; Hofman, Albert
2017-01-01
Large-scale genome-wide association results are typically obtained from a fixed-effects meta-analysis of GWAS summary statistics from multiple studies spanning different regions and/or time periods. This approach averages the estimated effects of genetic variants across studies. In case genetic effects are heterogeneous across studies, the statistical power of a GWAS and the predictive accuracy of polygenic scores are attenuated, contributing to the so-called ‘missing heritability’. Here, we describe the online Meta-GWAS Accuracy and Power (MetaGAP) calculator (available at www.devlaming.eu) which quantifies this attenuation based on a novel multi-study framework. By means of simulation studies, we show that under a wide range of genetic architectures, the statistical power and predictive accuracy provided by this calculator are accurate. We compare the predictions from the MetaGAP calculator with actual results obtained in the GWAS literature. Specifically, we use genomic-relatedness-matrix restricted maximum likelihood to estimate the SNP heritability and cross-study genetic correlation of height, BMI, years of education, and self-rated health in three large samples. These estimates are used as input parameters for the MetaGAP calculator. Results from the calculator suggest that cross-study heterogeneity has led to attenuation of statistical power and predictive accuracy in recent large-scale GWAS efforts on these traits (e.g., for years of education, we estimate a relative loss of 51–62% in the number of genome-wide significant loci and a relative loss in polygenic score R2 of 36–38%). Hence, cross-study heterogeneity contributes to the missing heritability. PMID:28095416
2013-01-01
为分析110 kV并网电源对电网安全稳定影响，提出构建考虑110 kV并网电源计算网络的原则，通过建立模拟简单2区域电网，从机理上分析使用考虑110 kV并网电源计算网络与使用220 kV及以上电压等级计算网络得到不同暂态稳定计算结论的原因。通过构建湖南电网考虑110 kV并网电源计算网络，并开展牌长Ⅰ，Ⅱ与艳宗Ⅱ线外送功率极限计算，表明考虑110 kV并网电源计算网络对暂态稳定水平有较大提高，建议使用考虑110 kV并网电源计算网络开展稳定计算。%To analyze influences of 110 kV power supply on safety and stability, principles of constructing calculation network including 110 kV power supplies are presented.The different results of transient stability are explained based on 110 kV and low calculation network and 220 kV and above calculation, through simulating simple 2-area power network.Then calculation network of Hunan power system including 110 kV and low power supply is constructed.And the transmission limit of section made of Paichang ⅠⅡ and YanzongⅡ is calculated.The result shows that the transient stability based on calculation network including 110 kV and low supplies is improved.It is suggested that the stability calculation should be conduceted based on 110 kV and above power supplies calculation network.
Dolly, S [Washington University School of Medicine, Saint Louis, MO (United States); University of Missouri, Columbia, MO (United States); Chen, H; Anastasio, M; Mutic, S; Li, H [Washington University School of Medicine, Saint Louis, MO (United States)
2015-06-15
Purpose: Local noise power spectrum (NPS) properties are significantly affected by calculation variables and CT acquisition and reconstruction parameters, but a thoughtful analysis of these effects is absent. In this study, we performed a complete analysis of the effects of calculation and imaging parameters on the NPS. Methods: The uniformity module of a Catphan phantom was scanned with a Philips Brilliance 64-slice CT simulator using various scanning protocols. Images were reconstructed using both FBP and iDose4 reconstruction algorithms. From these images, local NPS were calculated for regions of interest (ROI) of varying locations and sizes, using four image background removal methods. Additionally, using a predetermined ground truth, NPS calculation accuracy for various calculation parameters was compared for computer simulated ROIs. A complete analysis of the effects of calculation, acquisition, and reconstruction parameters on the NPS was conducted. Results: The local NPS varied with ROI size and image background removal method, particularly at low spatial frequencies. The image subtraction method was the most accurate according to the computer simulation study, and was also the most effective at removing low frequency background components in the acquired data. However, first-order polynomial fitting using residual sum of squares and principle component analysis provided comparable accuracy under certain situations. Similar general trends were observed when comparing the NPS for FBP to that of iDose4 while varying other calculation and scanning parameters. However, while iDose4 reduces the noise magnitude compared to FBP, this reduction is spatial-frequency dependent, further affecting NPS variations at low spatial frequencies. Conclusion: The local NPS varies significantly depending on calculation parameters, image acquisition parameters, and reconstruction techniques. Appropriate local NPS calculation should be performed to capture spatial variations of
Negative time delay of light by a gravitational concave lens
Nakajima, Koki; Asada, Hideki
2014-01-01
Gravitational lens models, some of which might act as if a concave lens, have been recently investigated by using a static and spherically symmetric modified spacetime metric that depends on the inverse distance to the $n$-th power [Kitamura, Nakajima and Asada, PRD 87, 027501 (2013)]. We reexamine the time delay of light in a gravitational concave lens as well as a gravitational convex one. The frequency shift due to the time delay is also investigated. We show that the sign of the time delay in the lens models is the same as that of the deflection angle of light. The size of the time delay decreases with increase in the parameter $n$. We discuss also possible parameter ranges that are relevant to pulsar timing measurements in our galaxy.
Safety levels for exposure of cornea and lens to very high-frequency ultrasound.
Silverman, R H; Lizzi, F L; Ursea, B G; Cozzarelli, L; Ketterling, J A; Deng, C X; Folberg, R; Coleman, D J
2001-09-01
Very high-frequency (50-MHz) ultrasound is widely used for imaging the anterior segment of the eye. Our aim was to determine whether exposures to ultrasound at and above those used in diagnostic imaging systems might cause bioeffects in ocular tissues. We characterized the output parameters of a polyvinylidene difluoride transducer using a needle hydrophone. We exposed sites on the cornea or lens of rabbits for up to 30 minutes at a 10-kHz pulse repetition frequency. Tissue obtained immediately or 24 hours after exposure was examined by light microscopy. A numeric model was implemented to calculate expected temperature elevations in the cornea and lens under experimental conditions. No tissue changes were observed directly or by slit lamp. Light microscopy showed no abnormalities attributable to ultrasound exposure. Simulations showed that even long-term exposures should produce temperature elevations of less than 1 degree C in both the cornea and lens. With the use of exposure parameters 4 to 5 orders of magnitude greater than encountered in a clinical situation, no tissue changes were observed. This is consistent with the small (0.2 degrees C) temperature rises computed in simulations. The lack of biological effects is attributable to the small dimensions of the focal zone, allowing rapid dissipation of heat, and the low total acoustic power produced by the transducer.
Niancheng Zhou
2014-08-01
Full Text Available The influence of electric vehicle charging stations on power grid harmonics is becoming increasingly significant as their presence continues to grow. This paper studies the operational principles of the charging current in the continuous and discontinuous modes for a three-phase uncontrolled rectification charger with a passive power factor correction link, which is affected by the charging power. A parameter estimation method is proposed for the equivalent circuit of the charger by using the measured characteristic AC (Alternating Current voltage and current data combined with the charging circuit constraints in the conduction process, and this method is verified using an experimental platform. The sensitivity of the current harmonics to the changes in the parameters is analyzed. An analytical harmonic model of the charging station is created by separating the chargers into groups by type. Then, the harmonic current amplification caused by the shunt active power filter is researched, and the analytical formula for the overload factor is derived to further correct the capacity of the shunt active power filter. Finally, this method is validated through a field test of a charging station.
Glasser, A; Campbell, M C
1999-06-01
The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner.
Elmholdt, Claus Westergård; Fogsgaard, Morten
2016-01-01
In this chapter, we will explore the dynamics of power in processes of creativity, and show its paradoxical nature as both a bridge and a barrier to creativity in organisations. Recent social psychological experimental research (Slighte, de Dreu & Nijstad, 2011) on the relation between power...... and creativity suggests that when managers give people the opportunity to gain power and explicate that there is reason to be more creative, people will show a boost in creative behaviour. Moreover, this process works best in unstable power hierarchies, which implies that power is treated as a negotiable...... and floating source for empowering people in the organisation. We will explore and discuss here the potentials, challenges and pitfalls of power in relation to creativity in the life of organisations today. The aim is to demonstrate that power struggles may be utilised as constructive sources of creativity...
A polycarbonate ophthalmic-prescription lens series.
Davis, J K
1978-08-01
Improvements in polycarbonate material, production techniques, and scratch-resistant coatings, combined with a process-oriented design, have resulted in a precision lens series. Surface quality is comparable to that of untreated glass ophthalmic lenses. The repeatability of the process results in closely controlled axial power and off-axis performance. For most lens prescriptions, the ANSI Z80.1 optical-center specifications for prescription accuracy are maintained through a total field of view of 40 deg for an 8-mm range of center-of-rotation distances. Off-axis astigmatism is controlled for near-point seeing. The lenses are both lighter and thinner than those of crown glass. A scratch-resistant coating reduces the reflections normally associated with high-index (1.586) materials. Impact resistance exceeds that required by ANSI Z80.7 and is many times that required by ANSI Z80.1.
Focusing properties of Gaussian Schell-model beams by an astigmatic aperture lens
Pan Liu-Zhan; Ding Chao-Liang
2007-01-01
This paper studies the focusing properties of Gaussian Schell-model (GSM) beams by an astigmatic aperture lens.It is shown that the axial irradiance distribution, the maximum axial irradiance and its position of focused GSM beams by an astigmatic aperture lens depend upon the astigmatism of the lens, the coherence of partially coherent light, the truncation parameter of the aperture and Fresnel number. The numerical calculation results are given to illustrate how these parameters affect the focusing property.
Sarracino, Marcello
1941-01-01
The present article deals with what is considered to be a simpler and more accurate method of determining, from the results of bench tests under approved rating conditions, the power at altitude of a supercharged aircraft engine, without application of correction formulas. The method of calculating the characteristics at altitude, of supercharged engines, based on the consumption of air, is a more satisfactory and accurate procedure, especially at low boost pressures.
Silveira, Fernando Henrique; Schroeder, Marco Aurelio de O.; Visacro Filho, Silverio; Soares Junior, Amilton [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Lightning Research Center - Nucleo de Desenvolvimento Cientifico e Tecnologico em Descargas Atmosfericas]. E-mail: lrc@cpdee.ufmg.br
2001-07-01
In this document the authors present the previous results of accomplished simulations through a brand new model to calculate the induced voltage by atmospheric discharges on power transmission lines. Through geometric data variation from the transmission line and discharge parameters, it is executed a sensibility analysis concerning to the relevant factors in order to define the levels of induced voltage in the transmission line. Finally, the work aims to evaluate this phenomenon importance in connection with 138 kv transmission lines.
Chen, Shuheng; Hu, Weihao; Chen, Zhe
2014-01-01
is to describe the topology of radial distribution networks with a clear logic and a small memory size. The strategies of compensating the equivalent currents of break-point branches and the reactive power outputs of PV-type DGs are presented on the basis of superposition theorem. Their formulations...
Antonio A. Martínez García
2015-04-01
Full Text Available La regulación de la tensión es el modo más elemental de control de los Sistemas Eléctricos de Potencia que mejora la estabilidad y la estabilidad transitoria. La introducción de reguladores de tensión muy rápidos facilita la capacidad del sistema de generar acciones que conserven su estabilidad (incremento del torque sincronizante. No obstante, estos dispositivos disminuyen el amortiguamiento del sistema. La forma más económica de mejorar el amortiguamiento de las oscilaciones mecánicas de las unidades generadoras se logra con la adición de un control suplementario agregado en el sistema de excitación, que se conoce como estabilizador de potencia (PSS, por sus siglas en inglés Power System Stabilizer. En el presente trabajo se utilizan las posibilidades del paquete PSAT para seleccionar la mejor ubicación y ajustar PSS en un sistema longitudinal sencillo de dos áreas, similar al caso del Sistema Eléctrico de la República de Cuba. Normally, voltage regulation is the primary mode of control, which improves voltage and transient stability. The introduction of generator´s fast voltage regulators improves Electrical Power Systems ability to generate synchronizing torque to maintain stability. These control devices have a negative effect in damping system oscillations. Supplementary control in generator’s voltage regulators (PSS is the most economic solution to improve system damping. This supplementary control is obtained using power system dampers. PSAT abilities are used in order to obtain setting of this supplementary control in a simple longitudinal two areas system, similar to Cuban Electric Power System.
1981-09-01
The purpose of this program was to study the physics of the ion-energy boosting electrostatic lens for collective ion acceleration in the Luce diode. Extensive work was done in preparation for experiments on the PI Pulserad 1150. Analytic work was done on the orbit of protons in a mass spectrometer and a copper stack for nuclear activation analysis of proton energy spectrum has been designed. Unfortunately, a parallel program which would provide the Luce diode for the collective ion acceleration experiment never materialized. As a result no experiments were actually performed on the Pulserad 1150.
Vysotskaya, Anna; Kolvakh, Oleg; Stoner, Greg
2016-01-01
The aim of this paper is to describe the innovative teaching approach used in the Southern Federal University, Russia, to teach accounting via a form of matrix mathematics. It thereby contributes to disseminating the technique of teaching to solve accounting cases using mutual calculations to a worldwide audience. The approach taken in this course…
Ryouhei eIshii
2014-06-01
Full Text Available Frontal midline theta rhythm (Fmθ appears widely distributed over medial prefrontal areas in EEG recordings, indicating focused attention. Although mental calculation is often used as an attention-demanding task, little has been reported on calculation-related activation in Fmθ experiments. In this study we used spatially filtered MEG and permutation analysis to precisely localize cortical generators of the magnetic counterpart of Fmθ, as well as other sources of oscillatory activity associated with mental calculation processing (i.e., arithmetic subtraction. Our results confirmed and extended earlier EEG/MEG studies indicating that Fmθ during mental calculation is generated in the dorsal anterior cingulate and adjacent medial prefrontal cortex. Mental subtraction was also associated with gamma event-related synchronization, as an index of activation, in right parietal regions subserving basic numerical processing and number-based spatial attention. Gamma event-related desynchronization appeared in the right lateral prefrontal cortex, likely representing a mechanism to interrupt neural activity that can interfere with the ongoing cognitive task.
Vysotskaya, Anna; Kolvakh, Oleg; Stoner, Greg
2016-01-01
The aim of this paper is to describe the innovative teaching approach used in the Southern Federal University, Russia, to teach accounting via a form of matrix mathematics. It thereby contributes to disseminating the technique of teaching to solve accounting cases using mutual calculations to a worldwide audience. The approach taken in this course…
Tan, Zhenyu; Xia, Yueyuan; Liu, Xiangdong; Zhao, Mingwen; Zhang, Liming
2009-04-01
A new calculation of the stopping powers (SP) and inelastic mean free paths (IMFP) for electrons in toluene at energies below 10 keV has been presented. The calculation is based on the dielectric model and on an empirical evaluation approach of optical energy loss function (OELF). The reliability for the evaluated OELFs of several hydrocarbons with available experimental optical data has been systematically checked. For toluene, using the empirical OELF, the evaluated mean ionization potential, is compared with that given by Bragg's rule, and the calculated SP at 10 keV is also compared with the Bethe-Bloch prediction. The present results for SP and IMFP provide an alternative basic data for the study on the energy deposition of low-energy electrons transport through toluene, and also show that the method used in this work may be a good one for evaluating the SP and IMFP for hydrocarbons.
[Intraocular lens implantation in developmental lens disorders in children].
Kanigowska, Krystyna; Grałek, Mirosława; Kepa, Beata; Chipczyńska, Barbara
2009-01-01
The pediatric cataract surgery in eyes with developmental disorders, stay with still considerable challenge. At children, the lasting vision development extorts necessity quick settlement of refraction defect formed after operation. The intraocular lens old boy with cataract in microspherophakia and 12 years old boy with cataract in lens with coloboma. One-piece flexible and rigid PMMA intraocular lens was placed with success at posterior chamber without scleral fixations and without using capsular tension ring in this cases. After 3 years of observation there were no decentration or dislocation of intraocular lens in both children. Authors concluded that in some cases posterior chamber intraocular lens implantation despite defective zonular or capsular support, can make up the effective method of surgical treatment without risk of early dislocation.
Cicero, R., E-mail: ciceror@unican.e [INESCO INGENIEROS S.L., Santander (Spain); Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain); Cicero, S. [Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain); Gorrochategui, I. [Centro Tecnologico de Componentes, Santander (Spain); Lacalle, R. [INESCO INGENIEROS S.L., Santander (Spain); Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain)
2010-01-15
Nuclear power plants are generally designed and inspected according to the ASME Code. This code indicates stress intensity (S{sub INT}) as the parameter to be used in the stress analysis of components. One of the particularities of S{sub INT} is that it always takes positive values, independently of the nature of the stress (tensile or compressive). This circumstance is relevant in the Fatigue Monitoring Systems used in nuclear power plants, due to the manner in which the different variable stresses are combined in order to obtain the final total stress range. This paper describes some situations derived from the application of the ASME Code, shows different ways of dealing with them and illustrates their influence on the evaluation of the fatigue usage factor through a case study.
Djukanovic, M. (Inst. ' Nikola Tesla' , Belgrade (Yugoslavia)); Sobajic, D.J.; Yohhan Pao (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Electrical Engineering and Applied Physics Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Computer Engineering and Science AI WARE inc., Cleveland, OH (United States))
1992-10-01
In heavily stressed power systems, post-fault transient voltage dips can lead to undesired tripping of industrial drives and large induction motors. The lowest transient voltage dips occur when fault clearing times are less than critical ones. In this paper, we propose a new iterative analytical methodology to obtain more accurate estimates of voltage dips at maximum angular swing in direct transient stability analysis. We also propose and demonstrate the possibility of storing the results of these computations in the associative memory (AM) system, which exhibits remarkable generalization capabilities. Feature-based models stored in the AM can be utilized for fast and accurate prediction of the location, duration and the amount of the worst voltage dips, thereby avoiding the need and cost for lengthy time-domain simulations. Numerical results obtained using the example of the New England power system are presented to illustrate our approach. (Author)
胡晓松; 张殷; 谢光彬; 肖先勇; 李长松
2015-01-01
Loop closing scenarios change with distributed generations connected to distribution network, which puts forward new requirement for the calculation of loop closing power flow. A loop closing power flow calculation algorithm of distribution network with PV nodes is proposed. For the weak ability of back-forward sweep method to deal with PV nodes and looped network, the improved sensitivity matrix is used to realize the processing of PV nodes with power correction, and based on the superposition principle, the calculation of loop closing power flow is realized with loop closing power flow compensation method. The algorithm performance is verified by IEEE 33-node test system, results show that the proposed algorithm can effectively solve the calculation problem of loop closing power flow in distribution network with PV nodes.%随着分布式电源(Distributed generation, DG)的接入，配电网合环场景发生改变，给配电网合环潮流计算提出了新的要求。以PV型DG为例，提出一种含PV节点的配电网合环潮流算法。针对前推回代法处理PV节点和环网能力弱的特点，利用改进灵敏度矩阵对PV 节点进行无功修正，实现对PV 节点的处理。依据叠加原理，用合环功率补偿法对合环端口节点进行功率补偿，从而实现配电网合环潮流计算。最后对IEEE 33节点测试系统进行仿真分析，结果表明该算法能够有效解决含PV节点的配电网合环潮流计算问题。
Calculation Method and Analysis for the Annual Power Generation of PV Façades in China
Shen Xu; ZhongMing Hu; Jian Kang; Wei Liao; Jing Huang
2014-01-01
The application of PV façades emerges greatly in recent years and however its calculation methods and analysis remains insufficient under the weather conditions of China. In such demand, this paper investigates PV façade in terms of PV electricity generation in different arrangements and weather conditions of four major cities in China. The calculation models for PV façade are developed and validated by comparing the results with the measured data from the field experiments. A parametric study is carried out to provide a reference for the optimal design of the PV façades. The results show that with various cities, building orientations, building forms, materials and arrangements of PV modules, there is a distinct difference in the electrical output energy of PV façades. Weather conditions play a very important role in terms of PV generation performance of PV façades.
Panoramic lens applications revisited
Thibault, Simon
2008-04-01
During the last few years, innovative optical design strategies to generate and control image mapping have been successful in producing high-resolution digital imagers and projectors. This new generation of panoramic lenses includes catadioptric panoramic lenses, panoramic annular lenses, visible/IR fisheye lenses, anamorphic wide-angle attachments, and visible/IR panomorph lenses. Given that a wide-angle lens images a large field of view on a limited number of pixels, a systematic pixel-to-angle mapping will help the efficient use of each pixel in the field of view. In this paper, we present several modern applications of these modern types of hemispheric lenses. Recently, surveillance and security applications have been proposed and published in Security and Defence symposium. However, modern hemispheric lens can be used in many other fields. A panoramic imaging sensor contributes most to the perception of the world. Panoramic lenses are now ready to be deployed in many optical solutions. Covered applications include, but are not limited to medical imaging (endoscope, rigiscope, fiberscope...), remote sensing (pipe inspection, crime scene investigation, archeology...), multimedia (hemispheric projector, panoramic image...). Modern panoramic technologies allow simple and efficient digital image processing and the use of standard image analysis features (motion estimation, segmentation, object tracking, pattern recognition) in the complete 360° hemispheric area.
Piszczor, M. F.; Brinker, D. J.; Flood, D. J.; Avery, J. E.; Fraas, L. M.; Fairbanks, E. S.; Yerkes, J. W.; O'Neill, M. J.
1991-01-01
A high-efficiency, lightweight space photovoltaic concentrator array is described. Previous work on the minidome Fresnel lens concentrator concept is being integrated with Boeing's 30 percent efficient tandem GaAs/GaSb concentrator cells into a high-performance photovoltaic array. Calculations indicate that, in the near term, such an array can achieve 300 W/sq m at a specific power of 100 W/kg. Emphasis of the program has now shifted to integrating the concentrator lens, tandem cell, and supporting panel structure into a space-qualifiable array. A description is presented of the current status of component and prototype panel testing and the development of a flight panel for the Photovoltaic Array Space Power Plus Diagnostics (PASP PLUS) flight experiment.
Low threshold and high efficiency solar-pumped laser with Fresnel lens and a grooved Nd:YAG rod
Guan, Zhe; Zhao, Changming; Yang, Suhui; Wang, Yu; Ke, Jieyao; Gao, Fengbin; Zhang, Haiyang
2016-11-01
Sunlight is considered as a new efficient source for direct optical-pumped solid state lasers. High-efficiency solar pumped lasers with low threshold power would be more promising than semiconductor lasers with large solar panel in space laser communication. Here we report a significant advance in solar-pumped laser threshold by pumping Nd:YAG rod with a grooved sidewall. Two-solar pumped laser setups are devised. In both cases, a Fresnel lens is used as the primary sunlight concentrator. Gold-plated conical cavity with a liquid light-guide lens is used as the secondary concentrator to further increase the solar energy concentration. In the first setup, solar pumping a 6mm diameter Nd:YAG rod, maximum laser power of 31.0W/m2 cw at 1064nm is produced, which is higher than the reported record, and the slope efficiency is 4.98% with the threshold power on the surface of Fresnel lens is 200 W. In the second setup, a 5 mm diameter laser rod output power is 29.8W/m2 with a slope efficiency of 4.3%. The threshold power of 102W is obtained, which is 49% lower than the former. Meanwhile, the theoretical calculating of the threshold power and slope efficiency of the solar-pumped laser has been established based on the rate-equation of a four-level system. The results of the finite element analysis by simulation software are verified in experiment. The optimization of the conical cavity by TraceProsoftware and the optimization of the laser resonator by LASCADare useful for the design of a miniaturization solar- pumped laser.
Load Flow Calculation of Electric Power System Based on MATLAB%基于MATLAB的电力系统潮流计算
毕永廷; 杨海波; 师秀凤
2016-01-01
通过应用MATLAB软件对给定的电力系统进行潮流计算。通过比较MATLAB程序、Simulink仿真和Matpower同一负荷变化情况下的潮流计算结果，结果满足系统要求，验证了三种方法的有效性。同时三种方法运算效率符合现在潮流计算的发展，为电网潮流计算开辟了新方向。%MATLAB is used to calculate the load flow of the electric system. By comparing the calculation results of MATLAB, Simulation and Matpower under the same load change, it is found that all the results meet the system requirements, thus the three methods' effectiveness is verified. And the calculation efficiency of the three methods conform to the development of modern load flow calculation, so these methods have opened up a new direction for power flow calculation.
Elimination of aniseikonia in monocular aphakia with a contact lens-spectacle combination.
Schechter, R J
1978-01-01
Correction of monocular aphakia with contact lenses generally results in aniseikonia in the range of 7--9%; with correction by intraocular lenses, aniseikonia is approximately 2%. We present a new method of correcting aniseikonia in monocular aphakics using a contact lens-spectacle combination. A formula is derived wherein the contact lens is deliberately overcorrected; this overcorrection is then neutralized by the appropriate spectacle lens, to be worn over the contact lens. Calculated results with this system over a wide range of possible situations consistently results in an aniseikonia of 0.1%.
CMB lens sample covariance and consistency relations
Motloch, Pavel; Hu, Wayne; Benoit-Lévy, Aurélien
2017-02-01
Gravitational lensing information from the two and higher point statistics of the cosmic microwave background (CMB) temperature and polarization fields are intrinsically correlated because they are lensed by the same realization of structure between last scattering and observation. Using an analytic model for lens sample covariance, we show that there is one mode, separately measurable in the lensed CMB power spectra and lensing reconstruction, that carries most of this correlation. Once these measurements become lens sample variance dominated, this mode should provide a useful consistency check between the observables that is largely free of sampling and cosmological parameter errors. Violations of consistency could indicate systematic errors in the data and lens reconstruction or new physics at last scattering, any of which could bias cosmological inferences and delensing for gravitational waves. A second mode provides a weaker consistency check for a spatially flat universe. Our analysis isolates the additional information supplied by lensing in a model-independent manner but is also useful for understanding and forecasting CMB cosmological parameter errors in the extended Λ cold dark matter parameter space of dark energy, curvature, and massive neutrinos. We introduce and test a simple but accurate forecasting technique for this purpose that neither double counts lensing information nor neglects lensing in the observables.
Integral freeform illumination lens design of LED based pico-projector.
Zhao, Shuang; Wang, Kai; Chen, Fei; Qin, Zong; Liu, Sheng
2013-05-01
In this paper, an illumination lens design for a LED-based pico-projector is presented. Different from the traditional illumination systems composed by lens group, the integral illumination lens consists of a total internal reflector (TIR) and a freeform surface. TIR acts as collimation lens and its top surface formed by a freeform surface reshapes the nonuniform circular light pattern generated by TIR to be rectangular and uniform. Diameter and height of the lens are 16 and 10 mm, respectively. An optimization method to deal with the problem of extended light source is also presented in detail in this paper. According to the simulation results of the final optimized lens, 77% (neglecting the effect of polarization) of the power of light source is collected on liquid crystal on silicon panel with a 16∶9 ratio and illumination uniformity achieves 92%.
Lens distortion elimination for improving measurement accuracy of fringe projection profilometry
Li, Kai; Bu, Jingjie; Zhang, Dongsheng
2016-10-01
Fringe projection profilometry (FPP) is a powerful method for three-dimensional (3D) shape measurement. However, the measurement accuracy of the existing FPP is often hindered by the distortion of the lens used in FPP. In this paper, a simple and efficient method is presented to overcome this problem. First, the FPP system is calibrated as a stereovision system. Then, the camera lens distortion is eliminated by correcting the captured images. For the projector lens distortion, distorted fringe patterns are generated according to the lens distortion model. With these distorted fringe patterns, the projector can project undistorted fringe patterns, which means that the projector lens distortion is eliminated. Experimental results show that the proposed method can successfully eliminate the lens distortions of FPP and therefore improves its measurement accuracy.
Design of wide field and high resolution video lens
Xiao, Ze-xin; Zhan, Binzhou; Han, Haimei
2009-11-01
Online detecting is increasingly used in industrial process for the requirement of product quality improving. It is a trend that the "machine detecting" with "machine version + computer intelligence" as new method replaces traditional manual "eye observation". The essential of "machine detecting" is that image of object being collected with high resolution video lens on sensor panel of photoelectric (CCD ,CMOS) and detecting result being automatically gained by computer after the image saved and processed. "Machine detecting" is developing rapidly with the universal reception by enterprises because of its fine accurateness, high efficiency and the real time. Video lens is one of the important components of machine version system. Requirements of wide field and high resolution enlarged the complexity of video lens design. In this paper a design case used in visible light with field diameter Φ32mm, β=-0.25× and NA'=0.15. We give design parameters of the video lens which obtained with theoretically calculating and Oslo software optimization: MTF>0.3 in full field and 215lp/mm, distortion <0.05%.This lens has an excellent optic performance to match with 1.3 million pixels 1/2"CCD, and a high performance price ratio for being consist of only 7 single lens in the way of 5 units.
Research on the Calculation Method of Light Shadow Impact in Wind Power Field%风电场光影影响计算方法研究
靳卫齐; 杨萌
2015-01-01
Wind power generation which doesn’t pollute environment is a new energy resource project that has good social and economic benefit.This paper firstly points out the main shortcomings of the formula for the calculation of light shadow in wind power field at present.It is considered that the influence distance is smaller when we use the solar elevation angle at noon to calculate it.Then the paper discusses the advantage and improvements of new calculation method recommended.Finally,the conception of light shadow influence scope is proposed,and the basis for location selection of blower is provided.%风力发电是一种不污染环境具有良好的社会效益和经济效益的新能源项目。本文首先指出目前风电场光影计算所采用公式存在的主要不足之处，认为利用正午时分太阳高度角计算光影影响距离偏小，之后探讨本文推荐的新计算方法的优点及改进之处，最终提出了光影影响范围的概念，为风机选址提供了依据。
Ariel Santos Fuentefria
2012-07-01
Full Text Available La integración de la energía eólica en los sistemas eléctricos puede provocar problemas de estabilidad ligados fundamentalmente a la variación aleatoria del viento y que se reflejan en la tensión y la frecuencia del sistema. Por lo que conocer el Límite de Potencia Eólica (LPE que puede insertarse en la red sin que esta pierda la estabilidad es un aspecto de extrema importancia, en el cual se han realizando métodos de cálculo para encontrar dicho límite. Estos métodos se desarrollan teniendo en cuenta las restricciones del sistema en estado estacionario, en estado dinámico o ambos. En el siguiente trabajo se desarrolla un método para el cálculo de LPE teniendo en cuenta las restricciones en estado estacionario del sistema. El método propuesto se basa en un análisis de flujo continuado, complementado con el método de Producción Mínima de Potencia Activa, desarrollado en la bibliografía. Se prueba en el sistema eléctrico de la Isla de la Juventud, Cuba y se usa elsoftware libre PSAT para la realización de estos estudios. The wind power insertion in the power system is an important issue and can create some instability problems in voltage and system frequency due to stochastic origin of wind. Know the Wind Power Limit is a very importantmatter. Existing In bibliography a few methods for calculation of wind power limit. The calculation is based in static constrains, dynamic constraints or both. In this paper is developed a method for the calculation of wind power limit using some adjust in the continuation power flow, and having into account the static constrains. The method is complemented with Minimal Power Production Criterion. The method is proved in the Isla de la Juventud Electric System. The software used in the simulations was the Power System Analysis Toolbox (PSAT.
Henry Bastidas Mora
2011-08-01
Full Text Available This article presents an analysis of electrical distribution theory for 60Hz-lines operating at low voltage, particularly underground lines and residential indoor installations. Such distribution lines’ behaviour is observed as a function of frequency to consider any advantages regarding the potential use of power transmission lines (PTL for transmitting telecommunication signals. A method for computing the secondary parameters is proposed which has been based on the primary parameters, namely inductance, capacitance, conductance and resistance. The secondary parameters so obtained were characteristic impedance, propagation constant (together with its real value and the attenuation constant. Conductor configurations, insulation materials and gauges commonly used in Colombia were verified for such low-voltage lines. A mathematical model is proposed as a theoretical tool for analysing and predicting characteristic impedance pattern and the attenuations which occur at high frequencies, thereby complementing our group’s previous work. Conclusions are drawn, together with a perspective regarding future work and applications.
Wittman, D; Dell'Antonio, I P; Becker, A C; Margoniner, V E; Cohen, J; Norman, D; Loomba, D; Squires, G; Wilson, G; Stubbs, C; Hennawi, J F; Spergel, D N; Boeshaar, P C; Clocchiatti, A; Hamuy, M; Bernstein, G; González, A; Guhathakurta, R; Hu, W; Seljak, U; Zaritsky, D
2002-01-01
The Deep Lens Survey (DLS) is a deep BVRz' imaging survey of seven 2x2 degree fields, with all data to be made public. The primary scientific driver is weak gravitational lensing, but the survey is also designed to enable a wide array of other astrophysical investigations. A unique feature of this survey is the search for transient phenomena. We subtract multiple exposures of a field, detect differences, classify, and release transients on the Web within about an hour of observation. Here we summarize the scientific goals of the DLS, field and filter selection, observing techniques and current status, data reduction, data products and release, and transient detections. Finally, we discuss some lessons which might apply to future large surveys such as LSST.
Study of power flow calculation based on Matpower%基于Matpower的潮流计算方法
徐恒娇; 王洪诚; 胡江航; 沈霞
2013-01-01
介绍了Matpower软件的基本操作方法，并通过实际分析和计算，说明了Matpower软件在电力系统分析中的优越性，同时介绍了Matpower软件应用简易、计算精度高、准确快速和直观明了等特点。%This paper introduces the basic operation method of the software Matpower, and based on the actual analysis and calculation, explains the superiority of the software Matpower. And at the same time the paper analyzes that Matpower has the characteristics of simple application, high accuracy, fast speed and intuitiveness.
Vanosdol, J G; Gemmen, R S; Liese, E A
2007-10-01
In recent years there has been significant interest in identifying carbon capturing technologies that can be applied to fossil fuel power generation plants.CO_{2} capture technologies seek to reduce the amount of CO_{2} that would normally be emitted into the atmosphere from the daily operation of these plants. In terms of system efficiency and operating costs, this carbon capture is expensive. Further, the additional equipment that would be used to capture CO_{2} emissions greatly adds to the complexity of the system. There has also been significant interest in coal based gas turbine fuel cell hybrid power plants. A hybrid power plant can have much greater system efficiency than a normal gas turbine power plant because the heat that is normally unused in a standalone solid oxide fuel cell (SOFC) is recovered and used to drive a power producing turbine. It is thought that the increased system efficiency of the hybrid system might compensate for the increased expense of performing carbon capture. In order to provide some analytical insight on this tradeoff we present a 100 MW class coal fired gas turbine SOFC hybrid power generation system. The hybrid system operates at a pressure ratio of 6, and uses heat recuperation and cathode air recirculation to control the SOFC inlet temperature and the temperature change across the SOFC. A carbon capture scheme is added to this system in order to calculate the relative energy cost in terms of system efficiency due to CO_{2} compression. The carbon capture is performed by burning the unused fuel from the SOFC in an isolated anode stream using pure O_{2} injection. The resulting heat that is generated from this process is then used to drive a secondary turbine that is placed in the anode exhaust stream where more work is extracted. With an isolated anode stream, the products of combustion from this secondary combustion process are mostly water and carbon dioxide. The water by-product is
LensTools: Weak Lensing computing tools
Petri, A.
2016-02-01
LensTools implements a wide range of routines frequently used in Weak Gravitational Lensing, including tools for image analysis, statistical processing and numerical theory predictions. The package offers many useful features, including complete flexibility and easy customization of input/output formats; efficient measurements of power spectrum, PDF, Minkowski functionals and peak counts of convergence maps; survey masks; artificial noise generation engines; easy to compute parameter statistical inferences; ray tracing simulations; and many others. It requires standard numpy and scipy, and depending on tools used, may require Astropy (ascl:1304.002), emcee (ascl:1303.002), matplotlib, and mpi4py.
上、卸卷车传动功率的计算与分析%Calculation and Analysis of Coil Car Drive Power
李毅飞
2015-01-01
文章分析了影响上、卸卷车传动功率的诸多因素，采用综合影响系数加以考虑，推导出上、卸卷车传动功率的近似计算公式。经现场验证，与生产实际值较吻合。%The paper analyzed various factors influencing drive power of coil car; it presented the derivation of approximate formula for calculating drive power by taking comprehensive effect coefficient into account;and it pointed out that the theoretical results were proven to be in consistent with actual values on site.
Sidorov, Aleksandr I.; Medvedeva, Yulia V.; Khanzhina, Olga A.
2016-10-01
The article deals with the calculation of setpoints for control systems insulation installed in all power distribution networks with voltage of 6 or 10 kV. It is shown that on the basis of fuzzy sets, the calculation of setpoints may be carried out even in the face of uncertainty. The efficiency of the system insulation monitoring based on measuring parameters of the electric network is largely determined by proper selection of the setpoint, i.e. the value of the insulation resistance of the network relative to the earth, in which it is necessary to disable a particular part of the network where a further reduction of the insulation resistance is unacceptable.
Sk, Mahasin Alam; Chen, Yingqian; Manzhos, Sergei
2016-08-01
We report a qualitative difference in molecular band structures and frontier orbital nodal structures in DFT calculations using GGA vs. hybrid functionals and Hartree Fock in molecules used in electrochemical power sources. This can have a significant effect in applications sensitive to redox potentials and to orbital overlaps (excitations, electron transfer rates) but for which the use of hybrid functionals is impractical, such as solids or interfaces used in electrochemical energy conversion and storage technologies. We show that correct band structures and nodal structures (ordering) of frontier orbitals can be obtained by applying a Hubbard correction to selected atomic states.
Teber, S
2016-01-01
We review the method of uniqueness which is a powerful technique for multi-loop calculations in higher dimensional theories with conformal symmetry. We use the method in momentum space and show that it allows a very transparent evaluation of a two-loop massless propagator Feynman diagram with a non-integer index on the central line. The result is applied to the computation of the optical conductivity of graphene at the infra-red Lorentz invariant fixed point. The effect of counter-terms is analysed. A brief comparison with the non-relativistic case is included.
A. A. Matvienko
2016-01-01
Full Text Available A methodology for determination of seismic accelerations in earth dams has been developed within the framework of seismic resistance wave theory. In this case we take into account an influence of the dam foundation and seismic wave emission into it. The methodology is based on numerical solution of the dynamic problem while using a finite difference method. A software program SGD “Determination of seismic acceleration in the earth dam” has been prepared on the basis of the developed methodology. The program allows to evaluate ordinates of calculation orthographic representations for acceleration throughout the dam height for all time moments. Thus, it is possible to obtain the most dangerous acceleration orthographic representations at direct and reverse seismic actions. The papers presents verification (compliance test of calculated and observed seismic accelerations for the rock-fill dam of the Dnestrovskaya Hydro-Electric Power Plant No 1. The observed seismic accelerations have been obtained during experimental explosions. The calculated seismic accelerations have been obtained in accordance with the proposed methodology for determination of seismic accelerations in the earth dams. A comparative analysis of calculation results with the data of field observations has demonstrated that a maximum difference between extreme accelerations obtained by calculation, and during field observations, do not exceed 10.11 % for the dam crest, and 6.56 % for its bottom. The obtained results permit to recommend the developed program for engineering calculations of seismic accelerations in the earth dams. The program application will make it possible to determine seismic acceleration in the earth dam with sufficient reliability.
Sánchez-Parcerisa, D; Gemmel, A; Jäkel, O; Rietzel, E; Parodi, K
2013-01-07
Previous calculations of the water-to-air stopping power ratio (s(w,)(air)) for carbon ion beams did not involve tracking of delta ray electrons, even though previous calculations with protons predict an effect up to 1%. We investigate the effect of the delta ray production threshold in s(w,)(air) calculations and propose an empirical expression which takes into account the effect of the delta ray threshold as well as the uncertainty in the mean ionization potentials (I-values) of air and water. The formula is derived from the results of Monte Carlo calculations using the most up-to-date experimental data for I-values and a delta ray production threshold of 10 keV. It allows us to reduce the standard uncertainty in s(w,)(air) below 0.8%, instead of the current 2% given in international protocols, which results in a reduction of the overall uncertainty for absolute dosimetry based on air-filled ionization chambers.
Henrice Junior, Edson; Goncalves, Alessandro da Cruz, E-mail: ejunior@nuclear.ufrj.br, E-mail: alessandro@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Departamento de Engenharia Nuclear; Palma, Daniel Arthur Pinheiro, E-mail: dapalma@cnen.gov.br [Comissao Nacional de Energia Nucleara (CNEN), Rio de Janeiro, RJ (Brazil)
2013-07-01
This paper presents an efficient method for calculating the reactivity using inverse point kinetic equation for subcritical systems by applying the Euler-MacLaurin summation formula to calculate the nuclear power history. In accordance with the accuracy of the numerical results, this method does not require a large number of points for calculation, providing accurate results with low computational cost. (author)
PKS 1830-211: A Possible Compound Gravitational Lens
Lovell, J. E. J.; Reynolds, J. E.; Jauncey, D. L.; Backus, P. R.; McCullock, P. M.; Sinclair, M. W.; Wilson, W. E.; Tzioumis, A. K.; Gough, R. G.; Ellingsen, S. P.; Phillips, C. J.; Preston, R. A.; Jones, D. L.
1996-01-01
Measurements of the properties of gravitational lenses have the power to tell us what sort of universe we live in. The brightest known radio Einstein ring/gravitational lens PKS 1830-211, whilst obscured by our Galaxy at optical wavelengths, has recently provided a lensing galaxy redshift of 0.89 through the detection of molecular absorption in the millimetre waveband.
Development of a ciliary muscle-driven accommodating intraocular lens
Hermans, Erik A.; Terwee, Thom T.; Koopmans, Steven A.; Dubbelman, Michiel; van der Heijde, Rob G. L.; Heethaar, Rob M.
2008-01-01
PURPOSE: To develop a ciliary muscle-driven accommodating intraocular lens (IOL) that has a large and predictable range of variable power as a step toward spectacle independence. SETTING: Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands. METHODS:
Development of a 3D finite element model of lens microcirculation
Vaghefi Ehsan
2012-09-01
Full Text Available Abstract Background It has been proposed that in the absence of a blood supply, the ocular lens operates an internal microcirculation system. This system delivers nutrients, removes waste products and maintains ionic homeostasis in the lens. The microcirculation is generated by spatial differences in membrane transport properties; and previously has been modelled by an equivalent electrical circuit and solved analytically. While effective, this approach did not fully account for all the anatomical and functional complexities of the lens. To encapsulate these complexities we have created a 3D finite element computer model of the lens. Methods Initially, we created an anatomically-correct representative mesh of the lens. We then implemented the Stokes and advective Nernst-Plank equations, in order to model the water and ion fluxes respectively. Next we complemented the model with experimentally-measured surface ionic concentrations as boundary conditions and solved it. Results Our model calculated the standing ionic concentrations and electrical potential gradients in the lens. Furthermore, it generated vector maps of intra- and extracellular space ion and water fluxes that are proposed to circulate throughout the lens. These fields have only been measured on the surface of the lens and our calculations are the first 3D representation of their direction and magnitude in the lens. Conclusion Values for steady state standing fields for concentration and electrical potential plus ionic and fluid fluxes calculated by our model exhibited broad agreement with observed experimental values. Our model of lens function represents a platform to integrate new experimental data as they emerge and assist us to understand how the integrated structure and function of the lens contributes to the maintenance of its transparency.
DESIGN FEATURES OF THE NEW CHISEL COMBINED AND CALCULATION NEEDS OF THE ENGINE POWER AT HIS WORK
Maslov G. G.
2015-05-01
Full Text Available The article presents technologies and design features of the proposed chisel combined unit, combining in a single pass over the field 3 operations: deep loosening, crumbling additional topsoil and alignment, fertilizing. Design features of such a subsoiller as the basis of the unit include a chisel on each rack, fixed at an angle of 15-25 degrees to the horizontal and lessons along the center line of the rack feet, and flat cutting fun-leveling, consisting of two coaxially bred drums equipped with ripper teeth securely fastened according to our patents and placed in 5-9 rows on the surface of the drums on the helix, with rows of teeth on both drums have the opposite direction. The teeth of the first drum are long by 5-9 cm than the second, the clearance between the teeth of the first and second drum does not exceed 1.5 cm, and the ends of the teeth between the first reel and the cylindrical surface of the second - 1 cm. Front legs each provided with a divider soil laid down by its center and related to the lower of its parts - the bit. The first reel is mounted to 5 cm clearance between it and the cylindrical surface of the soil, which improves process reliability. We have got analytical dependences of the required power for the engine of the tractor unit with the proposed change of the working speed and width at the optimum utilization traction tractor plowing 0.9. We have justified a preferred brand of domestic and foreign tractors for this purpose
Lightweight Inexpensive Ozone Lidar Telescope Using a Plastic Fresnel Lens
DeYoung, Russell J.; Notari, Anthony; Carrion, William; Pliutau, Denis
2014-01-01
An inexpensive lightweight ozone lidar telescope was designed, constructed and operated during an ozone lidar field campaign. This report summarizes the design parameters and performance of the plastic Fresnel lens telescope and shows the ozone lidar performance compared to Zemax calculations.
Effect of interface reflection in pseudophakic eyes with an additional refractive intraocular lens.
Schrecker, Jens; Zoric, Katja; Meßner, Arthur; Eppig, Timo
2012-09-01
To compare the surface reflections in a pseudophakic model eye with and without a monofocal additional refractive intraocular lens (add-on IOL). Department of Ophthalmology, Rudolf-Virchow-Klinikum Glauchau, Glauchau, and Experimental Ophthalmology, Saarland University, Homburg, Germany. Experimental study. The Liou and Brennan model eye was used to determine the retinal surface reflections in a pseudophakic model eye with and without an add-on IOL. The crystalline lens of the model eye was replaced by (1) a standard posterior chamber IOL (PC IOL) with a refractive power of 22.0 diopters (D) and (2) a PC IOL and an add-on IOL with refractive powers of 19.0 D and 2.5 D, respectively. To theoretically estimate the impact of the reflected images to visual impression, the signal-to-noise ratio (SNR) was calculated under 2 conditions: without and with straylight and double reflection effects. Compared with the pseudophakic model eye without an add-on IOL, the pseudophakic model eye with an add-on IOL showed no relevant differences in the SNR under both conditions. Findings indicate that implantation of monofocal add-on IOLs will not induce relevant additional disturbing glare compared with conventional pseudophakia. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
李苗; 邓长虹; 游佳斌; 周沁
2016-01-01
针对风电场出力的波动性使风电接入地区电网的随机性增强，并网点电压波动的频率和幅度变大，造成的电压稳定问题，以实际风电场的运行数据为基础，通过统计学方法分析风电场输出功率的波动特性，得到风功率波动率在不同时间尺度内的分布参数以及95%置信区间，并分析不同风电水平下的电压波动特性，在此基础上提出使用t location⁃scale分布函数对电压波动率的概率分布进行拟合，进而得出一种基于风功率波动特性以及仿射区间潮流算法的电压运行区间计算方法，通过该方法计算得到的电压运行区间反映了在风功率波动条件下未来一段时间内电力系统电压的运行区间，对风电接入系统的运行、控制及规划工作具有重要的指导意义。%The fluctuation of wind power plant can enhance the power grid randomness of wind power access region,and in⁃crease the frequency and amplitude of the voltage fluctuation at the connection point,which may cause the voltage stability problem. On the basis of the operating data of practical wind power plant,the statistical method is used to analyze the fluctuation charac⁃teristic of the wind power plant output power,so as to obtain the distribution parameters and 95% confidence interval of wind power fluctuation in different time scales,and analyze the voltage fluctuation characteristic under different wind power levels. On this basis,the t location⁃scale distribution function is used to fit the probability distribution of voltage fluctuation rate,and the voltage operating range calculation method based on wind power fluctuation characteristic and affine interval power flow algo⁃rithm is obtained. The voltage operating range calculated by this method reflects the possible operating voltage range of the electric power system within a period of time in the future under the condition of wind power fluctuation,and has an
Connexin hemichannels in the lens
Eric C Beyer
2014-02-01
Full Text Available The normal function and survival of cells in the avascular lens is facilitated by intercellular communication through an extensive network of gap junctions formed predominantly by three connexins (Cx43, Cx46, and Cx50. In expression systems, these connexins can all induce hemi-channel currents, but other lens proteins (e.g., pannexin1 can also induce similar currents. Hemichannel currents have been detected in isolated lens fiber cells. These hemichannels may make significant contributions to normal lens physiology and pathophysiology. Studies of some connexin mutants linked to congenital cataracts have implicated hemichannels with aberrant voltage-dependent gating or modulation by divalent cations in disease pathogenesis. Hemichannels may also contribute to age- and disease-related cataracts.
刘杨; 周明; 向萌; 张紫凡
2013-01-01
大型风电基地风电消纳的可行方案是跨区域直接送至负荷中心进行消化,由此产生大规模风电远距离输电的问题,进而对区域间最大输电能力(Total Transfer Capability,TTC)的计算提出新需求.针对大规模风电经直流外送的区域输电能力计算,结合风火打捆直流外送方式,建立了风电经直流外送的区域间TTC计算模型,并采用交直流交替迭代连续潮流算法进行求解.采用改进的IEEE 39节点系统进行测试,对大规模风电经交、直流2种外送方式下的TTC进行对比计算,并讨论了不同风电场出力情况及风火打捆比例对TTC的影响.结果表明:在既定网架结构下,需要协调考虑风火打捆比例和线路容量,在尽可能多地接纳风电的同时,使系统获得最大输电能力.%For the digestion of wind power generated in the large wind power bases, the feasible option is transferring the power to the load center directly cross regions, yet the new transfer format gives rise to the long distance power transmission of the large wind farms, which necessitates new demands for calculation of the total transfer capability (TTC) across regions. Aiming at the calculation of the TTC of the trans -regional HVDC transmission system for large-sized wind farms, and based on the format of the bundled transmission format of both thermal and wind power, this paper establishes a TTC calculation model considering that wind power delivered to another region by HVDC and uses the continuation power flow (CPF) algorithm based on AC/DC alternate iteration to find solutions. The modified IEEE 39 —bus system is used for the test, the TTC through AC and HVDC paths is calculated respectively and the influence of the wind power output and wind/fire bundling ratio is also discussed. The results indicate that under the established grid structure, it's necessary to consider wind fire bundling proportion and line capacity coordinately to ensure the system can
Szolnoki Gergely
2016-01-01
Full Text Available The main purpose of this consumer study was firstly to calculate the economic importance, in term of purchasing power, of visitors in the German wine growing region Rheingau, and secondly to examine their demographic and behavioural characteristics, as well as their the motivation using segmentation approach. In the framework of a face-to-face survey, conducted between April and May 2015, a total of 1,555 tourists were interviewed at 18 different locations in the Rheingau. Four wine tourist types were identified by using cluster analysis: 1 Wine and Rheingau lovers, who have a high interest in wine and visit the region several times a year; 2 wine-oriented tourists, who use the culinary offerings of the Rheingau with pleasure but do not come to the region very often; 3 new visitors, who come to the region mainly because of the nature and history; and 4 foreign tourists, who have less knowledge about the Rheingau and buy less wine in the region. With the help of the purchasing power calculation, we can state that approximately 18 % of the total production is purchased directly in the region by tourists.
Gravitational lens surveys with LOFAR
Wucknitz, O
2008-01-01
Deep surveys planned as a Key Science Project of LOFAR provide completely new opportunities for gravitational lens searches. For the first time do large-scale surveys reach the resolution required for a direct selection of lens candidates using morphological criteria. We briefly describe the strategies that we will use to exploit this potential. The long baselines of an international E-LOFAR are essential for this project.
Mody, Vino C. Jr
2006-01-01
Purpose: First, we intended to establish a method for sample preparation for measurement of ascorbate in whole rat and guinea pig lenses utilizing ultrafiltration and high performance liquid chromatography with ultraviolet radiation detection. Then, we aimed to investigate whether, in the albino rat, lens ascorbate concentration depends on solid dietary intake. Finally, we investigated if, in the pigmented guinea pig, lens ascorbate concentration may be elevated with drinkin...
Phakic Intraocular lens- a review
Cruz, Francisco Miguel
2015-01-01
Introduction: Intraocular refractive procedures with the implantation of a Phakic Intraocular lens have become a safe efficient and predictable alternative for treating high ametropias when the use of corneal photoablative procedures is not possible. The implantation of Phakic intraocular lens preservs the accomodative function,is a reversable refractive procedure, with minimal induction of higher order aberrations compaed with corneal photoablative procedures. Methods: An analytical review o...
Affect and Graphing Calculator Use
McCulloch, Allison W.
2011-01-01
This article reports on a qualitative study of six high school calculus students designed to build an understanding about the affect associated with graphing calculator use in independent situations. DeBellis and Goldin's (2006) framework for affect as a representational system was used as a lens through which to understand the ways in which…
Velzel, Chris
2014-01-01
A Course in Lens Design is an instruction in the design of image-forming optical systems. It teaches how a satisfactory design can be obtained in a straightforward way. Theory is limited to a minimum, and used to support the practical design work. The book introduces geometrical optics, optical instruments and aberrations. It gives a description of the process of lens design and of the strategies used in this process. Half of its content is devoted to the design of sixteen types of lenses, described in detail from beginning to end. This book is different from most other books on lens design because it stresses the importance of the initial phases of the design process: (paraxial) lay-out and (thin-lens) pre-design. The argument for this change of accent is that in these phases much information can be obtained about the properties of the lens to be designed. This information can be used in later phases of the design. This makes A Course in Lens Design a useful self-study book, and a suitable basis for an intro...
Chizhikova, Z.N.; Kalashnikov, A.G.; Kapranova, E.N.; Korobitsyn, V.E.; Manturov, G.N.; Tsiboulia, A.A.
1998-12-01
One of the important problems for ensuring the VVER type reactor safety when the reactor is partially loaded with MOX fuel is the choice of appropriate physical zoning to achieve the maximum flattening of pin-by-pin power distribution. When uranium fuel is replaced by MOX one provided that the reactivity due to fuel assemblies is kept constant, the fuel enrichment slightly decreases. However, the average neutron spectrum fission microscopic cross-section for {sup 239}Pu is approximately twice that for {sup 235}U. Therefore power peaks occur in the peripheral fuel assemblies containing MOX fuel which are aggravated by the interassembly water. Physical zoning has to be applied to flatten the power peaks in fuel assemblies containing MOX fuel. Moreover, physical zoning cannot be confined to one row of fuel elements as is the case with a uniform lattice of uranium fuel assemblies. Both the water gap and the jump in neutron absorption macroscopic cross-sections which occurs at the interface of fuel assemblies with different fuels make the problem of calculating space-energy neutron flux distribution more complicated since it increases nondiffusibility effects. To solve this problem it is necessary to update the current codes, to develop new codes and to verify all the codes including nuclear-physical constants libraries employed. In so doing it is important to develop and validate codes of different levels--from design codes to benchmark ones. This paper presents the results of the burnup calculation for a multiassembly structure, consisting of MOX fuel assemblies surrounded by uranium dioxide fuel assemblies. The structure concerned can be assumed to model a fuel assembly lattice symmetry element of the VVER-1000 type reactor in which 1/4 of all fuel assemblies contains MOX fuel.
Calculation Analysis on Power System Characteristics Under Random Excitation%随机激励下电力系统特性的计算分析
刘咏飞; 鞠平; 薛禹胜; 吴峰; 张建勇
2014-01-01
随着可再生能源发电和电动汽车的不断接入，随机激励对电力系统特性的影响日渐突出。为了研究电力系统在随机激励下的响应特性，首先，以可再生能源发电和电动汽车接入电网后所引起的功率波动作为随机激励，假设该激励的形式为高斯型白噪声，并基于单机无穷大系统，构造了带有随机功率激励项的非线性随机微分方程模型。其次，采用 Heun数值方法，分析了仿真计算步长、随机激励强度以及随机激励步长对系统功角响应的影响。最后，根据系统功角响应功率谱特性，从频域的角度分析了功率随机激励下的功角响应特性，获得了相应的结论。%With the steady integration of renewable generation and electrical vehicles into power systems,the dynamics of the power system under random factors is receiving ever-increasing concern.In order to discuss the dynamic responses of the power system under random excitation,a nonlinear stochastic differential equation (SDE) model for one machine and infinite bus (OMIB) system is built,where the power fluctuation of renewable energy and electrical vehicles are treated as Gaussian white noise.Then the Heun numerical method is applied to the SDE to calculate the dynamics of rotor angle under random disturbance.The calculation step is firstly changed to study the numerical stability of the Heun method.The random excitations with different intensities are also applied to the SDE,and the impact of random excitation on the dynamics of rotor angle is analyzed.The effect of the time interval of random excitation on the rotor angle is also studied.Finally,according to the characteristics of the corresponding power spectrum,some conclusions of the impact of random excitation on the dynamics of the rotor angle are gained.
Chitah: Strong-gravitational-lens hunter in imaging surveys
Chan, James H. H.; Suyu, Sherry H.; Chiueh, Tzihong; More, Anupreeta; Marshall, Philip J.; Coupon, Jean; Oguri, Masamune; Price, Paul
2015-07-07
Strong gravitationally lensed quasars provide powerful means to study galaxy evolution and cosmology. Current and upcoming imaging surveys will contain thousands of new lensed quasars, augmenting the existing sample by at least two orders of magnitude. To find such lens systems, we built a robot, Chitah, that hunts for lensed quasars by modeling the configuration of the multiple quasar images. Specifically, given an image of an object that might be a lensed quasar, Chitah first disentangles the light from the supposed lens galaxy and the light from the multiple quasar images based on color information. A simple rule is designed to categorize the given object as a potential four-image (quad) or two-image (double) lensed quasar system. The configuration of the identified quasar images is subsequently modeled to classify whether the object is a lensed quasar system. We test the performance of Chitah using simulated lens systems based on the Canada–France–Hawaii Telescope Legacy Survey. For bright quads with large image separations (with Einstein radius ${r}_{\\mathrm{ein}}\\gt 1\\buildrel{\\prime\\prime}\\over{.} 1$) simulated using Gaussian point-spread functions, a high true-positive rate (TPR) of $\\sim 90\\%$ and a low false-positive rate of $\\sim 3\\%$ show that this is a promising approach to search for new lens systems. We obtain high TPR for lens systems with ${r}_{\\mathrm{ein}}\\gtrsim 0\\buildrel{\\prime\\prime}\\over{.} 5$, so the performance of Chitah is set by the seeing. We further feed a known gravitational lens system, COSMOS 5921+0638, to Chitah, and demonstrate that Chitah is able to classify this real gravitational lens system successfully. Our newly built Chitah is omnivorous and can hunt in any ground-based imaging surveys.
The effect of lens parameters on the development of the primary angle-closure glaucoma
Zhaohui Feng; Naixue Sun; Aiyi Zhou; Donggang Han; Yun Long; Zhao Wang; Xiaohua Wang
2007-01-01
Objective:To investigate the role the lens dimensions played on the pathogenesis of primary angle-closure glaucoma.Methods:38 eyes of 20 patients with primary angle-closure glaucoma (PACG) and 35 eyes of 22 normal individuals without ocular abnormalities were examined. The anatomical parameters of the lens and other structures of the anterior segment were calculated using B ultrasound, computer image processing and ultrasound biomicroscopy (UBM). The parameters were compared between the patients and normal subjects. Correlation analysis was used to determine the relationship between the radii of curvature of the anterior lens surface (RCALS) and the other parameters of the anterior segment. Results:Compared with the normal eyes, the eyes of PACG had thicker lens, steeper curvature of anterior lens surface, decreased depth of the anterior chamber, narrower chamber angle, and more anterior position of the ciliary bodies and lens. All these differences were significant(P ＜ 0.05 or P ＜ 0.01). In the PACG group, the RCALS had significantly negative correlation with the central and peripheral lens thickness (P ＜ 0.01 and P ＜ 0.05 respectively), and had positive correlation with relative lens position, anterior chamber depth (ACD), angle-open distance at 500 um(AOD500), trabecular iris angle(TIA) and trabecular ciliary processes distance(TCPD, P ＜ 0.05 or P ＜ 0.01 ). Conclusion:The occurrence of PACG is relevant to the abnormal anatomical structures of the anterior segment. Among all factors, the lens parameters play an important role in the pathogenesis. Increased lens thickness, relative more anterior position of lens, especially steepened curvature of anterior lens surface are predisposing factors of the pathologic phenomenon in PACG including pupillary blockage, shallow anterior chamber, secondary closure of chamber angle and elevation of intraocular pressure.
Nonlinear laser pulse response in a crystalline lens.
Sharma, R P; Gupta, Pradeep Kumar; Singh, Ram Kishor; Strickland, D
2016-04-01
The propagation characteristics of a spatial Gaussian laser pulse have been studied inside a gradient-index structured crystalline lens with constant-density plasma generated by the laser-tissue interaction. The propagation of the laser pulse is affected by the nonlinearities introduced by the generated plasma inside the crystalline lens. Owing to the movement of plasma species from a higher- to a lower-temperature region, an increase in the refractive index occurs that causes the focusing of the laser pulse. In this study, extended paraxial approximation has been applied to take into account the evolution of the radial profile of the Gaussian laser pulse. To examine the propagation characteristics, variation of the beam width parameter has been observed as a function of the laser power and initial beam radius. The cavitation bubble formation, which plays an important role in the restoration of the elasticity of the crystalline lens, has been investigated.
Broadband Wide Angle Lens Implemented with Dielectric Metamaterials
Anthony Starr
2011-08-01
Full Text Available The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide field of view. Here we apply these techniques to a lesser-known refractive Luneburg lens and implement the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric. In addition, we investigate the aberrations introduced by various approximations made in the implementation of the lens. The resulting design approach has improved mechanical strength with small aberrations and is ideally suited to implementation at infrared and visible wavelengths.
Broadband Wide Angle Lens Implemented with Dielectric Metamaterials
Hunt, John; Kundtz, Nathan; Landy, Nathan; Nguyen, Vinh; Perram, Tim; Starr, Anthony; Smith, David R.
2011-01-01
The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide field of view. Here we apply these techniques to a lesser-known refractive Luneburg lens and implement the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric. In addition, we investigate the aberrations introduced by various approximations made in the implementation of the lens. The resulting design approach has improved mechanical strength with small aberrations and is ideally suited to implementation at infrared and visible wavelengths. PMID:22164056
Thermal optical path difference analysis of the telescope correct lens assembly
Hsu, Ming-Ying; Chang, Shenq-Tsong; Huang, Ting-Ming
2012-12-01
The effect of correct lens thermal optical path difference (OPD) on the optical performance of the Cassegrain telescope system is presented. The correct lens assembly includes several components such as a set of correct lenses, lens mount, spacer, mount barrel, and retainer. The heat transfer from the surrounding environment to the correct lens barrel will cause optical system aberration. The temperature distribution of the baffle is from 20.546°C to 21.485°C. Meanwhile, the off-axis ray's path of the OPD has taken the lens incidence point and emergence point into consideration. The correct lens temperature distribution is calculated by the lens barrel heat transfer analysis; the thermal distortion and stress are solved by the Finite Element Method (FEM) software. The temperature distribution is weighted to each incidence ray path, and the thermal OPD is calculated. The thermal OPD on the Z direction is transferred to optical aberration by fitting OPD into a rigid body motion and the Zernike polynomial. The aberration results can be used to evaluate the thermal effect on the correct lens assembly in the telescope system.
Zhao, Cunhua; Liang, Huiqin; Cui, Dongqing; Hong, Xinhua; Wei, Daling; Gao, Changliu
2011-08-01
In the ultralight or ultrathin applied domain of zoom lens, the traditional glass / plastic lens is limited for manufacture technology or cost. Therefore, a liquid lens was put forward to solve the problems. The liquid zoom lens has the merits of lower cost, smaller volume, quicker response, lower energy consumption, continuous zoom and higher accuracy. In liquid zoom lens the precise focal length is obtained by the contact angle changing to affect the curvature radius of interface. In our works, the relations of the exerted voltage, the contact angle, the curvature radius and the focal length were researched and accurately calculated. The calculation of the focal length provides an important theoretical basis for instructing the design of liquid zoom lens.
Simulation of a Laue lens with bent Ge(111) crystals
Valsan, Vineeth; Frontera, Filippo; Liccardo, Vincenzo; Caroli, Ezio; Stephen, John B
2015-01-01
In the context of Laue project for focusing hard X-/ soft gamma-rays, an entire Laue lens, using bent Ge(111) crystal tiles, with 40 meters curvature radius, is simulated with a focal length of 20 meters. The focusing energy band is between 80 keV and 600 keV. The distortion of the output image of the lens on the focal plane due to the effect of crystal tile misalignment as well as the radial distortion arising from the curvature of the crystal is discussed in detail. Expected detection efficiency and instrument background is also estimated. Finally the sensitivity of the Laue lens is calculated. A quantitative analysis of the results of these simulation is also presented.
The 2010 IODC lens design problem: the green lens
Juergens, Richard C.
2010-08-01
The lens design problem for the 2010 IODC is to design a 100 mm focal length lens in which every optical surface has the same radius of curvature, positive or negative, or is plano. The lens is used monochromatically at 532 nm and is made of only Schott N-BK7 glass. The goal of the problem is to maximize the product of the semi-field of view and the entrance pupil diameter while holding the distortion to within +/-5% and the RMS wavefront error to <= 0.07 wave within the field of view. There were 37 entries from eight different countries. Four different commercial lens design programs were used, along with two custom, in-house programs. The number of lens elements in the entries ranged from 3 to 64. The overall length of the lenses varied from 105 mm to 3.6 km. The winning entry had an entrance pupil diameter of 81.3 mm and a semi-field of view of 43.5° for a merit function product of 3537.
Dou, Wenbin; Sun, Zhong Liang; Zeng, G.
1998-11-01
integrated antennas have the advantages of low cost and can be readily mass produced using standard IC fabrication processes. However, integrated antennas suffer from the surface wave effect at millimeter waves. One of the ways to avoid this problem is to integrate the antennas on a dielectric lens. This structure does not support surface-waves and tend to radiate most of their power into the dielectric side making the pattern unidirectional on high dielectric constant lenses. The dielectric lens also provides mechanical rigidity and thermal stability. There are various dielectric lenses which can be used for receiver application. Among them the extended hemispherical lens is very practical, since it can synthesize other lenses such as hemispherical, hyperhemispherical, or ellipsoidal simply by varying the extension length behind the hemispherical position. In reference five, investigation on such antenna/lens system is presented. In reference 6, slot- ring antennas on dielectric lens is investigated. In many applications the extended hemispherical lens/objective lens antenna system is more attractive, because it can provide higher gain and may be used in imaging system. On the other hand, monopulse direction-finding techniques are currently the most accurate and rapid method for locating a target electronically. This antenna system can also be used as monopulse antenna. However, the treatments on such antenna system are not presented yet. In this paper, the radiation pattern of the antenna system fed by double-slot antenna are computed using ray-tracing and diffraction integration methods. Although the double-slot antenna is used as feed antenna, other antenna such as slot-ring, bow-tie antenna can be used too.
Novel switching mode in a vertically aligned liquid crystal contact lens.
Syed, Ishtiaque M; Kaur, Sarabjot; Milton, Harry E; Mistry, Devesh; Bailey, James; Morgan, Philip B; Jones, J Cliff; Gleeson, Helen F
2015-04-20
Liquid crystal (LC) contact lenses are emerging as an exciting technology for vision correction. A homeotropically (vertical) aligned LC lens is reported that offers improved optical quality and simplified construction techniques over previously reported LC contact lens designs. The lens has no polarization dependence in the off state and produces a continuous change in optical power of up to 2.00 ± 0.25 D with a voltage applied. The variation in optical power results from the voltage-induced change in refractive index of the nematic LC layer, from 1.52 to a maximum of 1.72. One device substrate is treated with an alignment layer that is a mixture of planar and homeotropic polyimides, rubbed to induce a preferred director orientation in the switched state. Defects that could occur during switching are thus avoided and the lens exhibits excellent optical quality with a continuous variation in focal power.
SimpleCalculation Method of Belt Conveyor Power%皮带机功率的简易计算方法
谷俊斐
2013-01-01
This article describes the arrangement of the belt conveyor , comes up with a simple method of belt conveyor pow-er by analyzing the drive roller structure .The calculation method is simple , easy to grasp and effective .%本文简要介绍了皮带机的布置形式，通过分析皮带机传动滚筒轴的组成结构，提出了皮带机传动滚筒轴功率的简易计算方法，该计算方法简单明了，易于掌握，为皮带机的设计提供了有效的参考方法。
Delto, Ralf; Winterholer, Benoit; Bender, Dieter [AREVA NP, Erlangen (Germany); Kierkegaard, Jesper [Vattenfall Nuclear Fuel AB, Vallingby (Sweden); Loberg, John [Uppsala Univ. (Sweden). Dept. of Applied Nuclear Physics
2010-05-15
For a deeper investigation of the pellet cladding interaction (PCI) phenomenon in BWRs a detailed knowledge of the pin power distribution in the vicinity of the control blade (CB) tip is required. The spatial resolution of nodal-core simulators like MICROBURN-B2 is normally not fine enough to give reliable information on the linear heat generation rate (LHGR) on a scaling of 1 cm and is not capable of describing the control rod handle precisely. Such fine-resolution LHGR calculations have been performed with MCNP in order to better understand the PCI phenomenon in BWRs. Two cases have been studied which correspond to two loading strategies in two different plants. These cases also have different CB geometry, different burnup of the fuel assemblies (FA) in the controlled cell and different void level. (orig.)
Photovoltaic power plants: production calculation
Cirillo, E.; Lazzarin, R.
Rational sizing of a photovoltaic plant requires a good evaluation of the obtainable electric energy as a function of the many meteorological and plant parameters. A computing procedure is described in detail together with a fully developed numerical example. The procedure is based on monthly usability. It is reliable and it allows designers to take into account the influence of the main plant parameters within rather wide ranges.
Björk, Peter; Knöös, Tommy; Nilsson, Per
2004-10-07
The aim of the present study was to investigate three different detector types (a parallel-plate ionization chamber, a p-type silicon diode and a diamond detector) with regard to output factor measurements in degraded electron beams, such as those encountered in small-electron-field radiotherapy and intraoperative radiation therapy (IORT). The Monte Carlo method was used to calculate mass collision stopping-power ratios between water and the different detector materials for these complex electron beams (nominal energies of 6, 12 and 20 MeV). The diamond detector was shown to exhibit excellent properties for output factor measurements in degraded beams and was therefore used as a reference. The diode detector was found to be well suited for practical measurements of output factors, although the water-to-silicon stopping-power ratio was shown to vary slightly with treatment set-up and irradiation depth (especially for lower electron energies). Application of ionization-chamber-based dosimetry, according to international dosimetry protocols, will introduce uncertainties smaller than 0.3% into the output factor determination for conventional IORT beams if the variation of the water-to-air stopping-power ratio is not taken into account. The IORT system at our department includes a 0.3 cm thin plastic scatterer inside the therapeutic beam, which furthermore increases the energy degradation of the electrons. By ignoring the change in the water-to-air stopping-power ratio due to this scatterer, the output factor could be underestimated by up to 1.3%. This was verified by the measurements. In small-electron-beam dosimetry, the water-to-air stopping-power ratio variation with field size could mostly be ignored. For fields with flat lateral dose profiles (>3 x 3 cm2), output factors determined with the ionization chamber were found to be in close agreement with the results of the diamond detector. For smaller field sizes the lateral extension of the ionization chamber hampers
RF Lens-Embedded Massive MIMO Systems: Fabrication Issues and Codebook Design
Kwon, Taehoon; Lim, Yeon-Geun; Min, Byung-Wook; Chae, Chan-Byoung
2016-07-01
In this paper, we investigate a radio frequency (RF) lens-embedded massive multiple-input multiple-output (MIMO) system and evaluate the system performance of limited feedback by utilizing a technique for generating a suitable codebook for the system. We fabricate an RF lens that operates on a 77 GHz (mmWave) band. Experimental results show a proper value of amplitude gain and an appropriate focusing property. In addition, using a simple numerical technique--beam propagation method (BPM)--we estimate the power profile of the RF lens and verify its accordance with experimental results. We also design a codebook--multi-variance codebook quantization (MVCQ)--for limited feedback by considering the characteristics of the RF lens antenna for massive MIMO systems. Numerical results confirm that the proposed system shows significant performance enhancement over a conventional massive MIMO system without an RF lens.
Probabilistic Optimal Power Flow Calculation Based on Digital Nets Method%基于数字网系方法的概率最优潮流计算
潘雄; 张龙; 黄家栋; 王莉莉; 吴瑞华
2015-01-01
风电场和光伏电站的大规模接入使得在进行电力系统最优潮流计算时需要考虑风电场和光伏电站出力的随机性。传统的蒙特卡洛法耗时长、占用内存大，文中提出一种利用数字网系(DN)的采样值具有等分布这一特性来改善输入随机变量分布空间覆盖程度的方法，并将该方法用于含风电场和光伏电站的电力系统概率最优潮流计算中。以 IEEE 30节点系统对所提方法的准确性与有效性进行了验证，仿真结果表明：DN 方法可以较好地估计输出随机变量的概率分布，能有效地处理电力市场中的不确定性问题。将该方法用于 IEEE 300节点系统，研究了系统接入不同容量光伏电站对节点电价的影响。同时，还将风电场和光伏混合系统与单独风电场系统进行对比，得到前者的节点电价、网损和支路功率波动更小的结论。%With large-scale integration of wind farms and photovoltaic plants into the power system,it becomes necessary to take the wind power and photovoltaic power uncertainty into consideration during optimal power flow (OPF) calculation.The traditional Monte Carlo simulation method cannot be used for the thousands of stochastic simulations required to achieve a rational result.Hence the digital nets (DN) method with equivalent distribution sample values is proposed to improve the sample value coverage of random variable input spaces.And the method is used in the OPF calculation of power system containing wind farms and photovoltaic plants.The accuracy and validity of the proposed method tested on an IEEE 30-bus system and the simulation results show that the proposed method has the advantages of fast computation and high accuracy while capable of estimating the probability distribution of the output random variables and dealing with the uncertainties in the electricity market.Then the DN method is applied to an IEEE 300-bus system to study the influence
Three-dimensional calculations for a 4 kA, 3.5 MV, 2 microsecond injector with asymmetric power feed
Thomas P. Hughes
1999-11-01
Full Text Available The DARHT-2 accelerator under construction at Los Alamos National Laboratory requires a long flattop (2μs 2–4 kA, 3.5 MV, low-emittance electron beam source. The injector is being constructed at Lawrence Berkeley National Laboratory and consists of a large-area thermionic cathode mounted atop a vertical column. The 90° bend between the horizontally emitted beam and the column produces dipole and higher-pole fields which must be corrected. In addition, the fast rise of the current flowing into the vacuum tank excites rf modes which cause transverse oscillations of the beam centroid. We have modeled these effects with the 3D electromagnetic code LSP. The code has models for pulsed power transmission lines, space-charge-limited emission and transport of charged particles, externally applied magnetic fields, and frequency-dependent absorption of rf. We calculate the transverse displacement of the beam as a function of time during the current pulse, and the positioning and thickness of ferrite absorber needed to damp the rf modes. The numerical results are compared to analytic calculations.
Fonseca, A. C.
1990-02-01
Four-body integral equations are used to calculate the binding energy of 4He as well as dd → dd and dd → p 3H amplitudes using a single term separable nucleon-nucleon potential in channels 1S 0 and 3S 1- 3D 1, together with the energy dependent pole expansion to set up an N term representation of all (3)+1 subamplitudes of interest. The (2)+(2) subamplitudes are treated exactly by convolution. The 4He binding energy is obtained from the exact solution of the equations. In the scattering region first order perturbation theory is used to separate the contribution of the s-wave components of the N-N t-matrix and s- and p-wave three-nucleon channels to the tour-nucleon Kernel, from the contribution of d-wave two- and three-nucleon channel components that result from the tensor-force. Cross sections and analysing powers are calculated using all positive and negative parity four-body amplitudes with total angular momentum J⩽4. Comparison with data is presented.
Parameters measurement of rigid gas permeable contact lens based on optical coherence tomography
Zhu, Dexi; Shen, Meixiao; Li, Yiyu
2012-10-01
Spectral domain optical coherence tomography (OCT) was developed in order to measure the geometric parameters of rigid gas permeable (RGP) contact lens. With custom designed OCT system, an ultra-high axial resolution of 3.3 μm in lens was achieved. The OCT image was corrected to eliminate the optical distortion and actual surfaces of lens were shown in contour map. Central thickness, lens diameter, base curve and front surface curvature at optical zone were calculated from the contour map. The results match well with the real values measured by conventional instruments. Our research indicates that OCT can be used to test the RGP lens in a simple and exact way.
Saito, Kazuo; Shimbori, Toshiki; Draxler, Roland
2015-01-01
The World Meteorological Organization (WMO) convened a small technical task team of experts to produce a set of meteorological analyses to drive atmospheric transport, dispersion and deposition models (ATDMs) for the United Nations Scientific Committee on the Effects of Atomic Radiation's assessment of the Fukushima Daiichi Nuclear Power Plant (DNPP) accident. The Japan Meteorological Agency (JMA) collaborated with the WMO task team as the regional specialized meteorological center of the country where the accident occurred, and provided its operational 5-km resolution mesoscale (MESO) analysis and its 1-km resolution radar/rain gauge-analyzed precipitation (RAP) data. The JMA's mesoscale tracer transport model was modified to a regional ATDM for radionuclides (RATM), which included newly implemented algorithms for dry deposition, wet scavenging, and gravitational settling of radionuclide aerosol particles. Preliminary and revised calculations of the JMA-RATM were conducted according to the task team's protocol. Verification against Cesium 137 ((137)Cs) deposition measurements and observed air concentration time series showed that the performance of RATM with MESO data was significantly improved by the revisions to the model. The use of RAP data improved the (137)Cs deposition pattern but not the time series of air concentrations at Tokai-mura compared with calculations just using the MESO data. Sensitivity tests of some of the more uncertain parameters were conducted to determine their impacts on ATDM calculations, and the dispersion and deposition of radionuclides on 15 March 2011, the period of some of the largest emissions and deposition to the land areas of Japan. The area with high deposition in the northwest of Fukushima DNPP and the hotspot in the central part of Fukushima prefecture were primarily formed by wet scavenging influenced by the orographic effect of the mountainous area in the west of the Fukushima prefecture.
Tinting of intraocular lens implants
Zigman, S.
1982-06-01
Intraocular lens (IOL) implants of polymethyl methacrylate (PMMA) lack an important yellow pigment useful as a filter in the visual process and in the protection of the retina from short-wavelength radiant energy. The ability to produce a yellow pigment in the PMMA used in IOL implants by exposure to near-ultraviolet (UV) light was tested. It was found that the highly cross-linked material in Copeland lens blanks was tinted slightly because of this exposure. The absorptive properties of lens blanks treated with near-UV light in this way approached that of the absorptive properties of human lenses. This finding shows that it is possible to alter IOL implants simply so as to induce a pale-yellow pigment in them to improve the visual process and to protect the retinas of IOL users.
International rigid contact lens prescribing.
Efron, Nathan; Morgan, Philip B; Helland, Magne; Itoi, Motozumi; Jones, Deborah; Nichols, Jason J; van der Worp, Eef; Woods, Craig A
2010-06-01
Rigid lenses have been fitted less since the introduction of soft lenses nearly 40 years ago. Data that we have gathered from annual contact lens fitting surveys conducted in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA between 2000 and 2008 facilitate an accurate characterization of the pattern of the decline of rigid lens fitting during the first decade of this century. There is a trend for rigid lenses to be utilized primarily for refitting those patients who are already successful rigid lens wearers-most typically older females being refit with higher Dk materials. Rigid lenses are generally fitted on a full-time basis (four or more days of wear per week) without a planned replacement schedule. Orthokeratology is especially popular in the Netherlands, but is seldom prescribed in the other countries surveyed.
Marshall, P.
2005-01-03
Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ''piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.
Algebraic Lens Distortion Model Estimation
Luis Alvarez
2010-07-01
Full Text Available A very important property of the usual pinhole model for camera projection is that 3D lines in the scene are projected to 2D lines. Unfortunately, wide-angle lenses (specially low-cost lenses may introduce a strong barrel distortion, which makes the usual pinhole model fail. Lens distortion models try to correct such distortion. We propose an algebraic approach to the estimation of the lens distortion parameters based on the rectification of lines in the image. Using the proposed method, the lens distortion parameters are obtained by minimizing a 4 total-degree polynomial in several variables. We perform numerical experiments using calibration patterns and real scenes to show the performance of the proposed method.
Liquid-crystal intraocular adaptive lens with wireless control.
Simonov, Aleksey N; Vdovin, Gleb; Loktev, Mikhail
2007-06-11
We present a prototype of an adaptive intraocular lens based on a modal liquid-crystal spatial phase modulator with wireless control. The modal corrector consists of a nematic liquid-crystal layer sandwiched between two glass substrates with transparent low- and high-ohmic electrodes, respectively. Adaptive correction of ocular aberrations is achieved by changing the amplitude and the frequency of the applied control voltage. The convex-shaped glass substrates provide the required initial focusing power of the lens. A loop antenna mounded on the rim of the lens delivers an amplitude-modulated radio-frequency control signal to the integrated rectifier circuit that drives the liquid-crystal modal corrector. In vitro measurements of a 5-mm clear aperture prototype with an initial focusing power of +12.5 diopter, remotely driven by a radio-frequency control unit at ~6 MHz, were carried out using a Shack-Hartmann wavefront sensor. The lens based on a 40-mum thick liquid-crystal layer allows for an adjustable defocus of 4 waves, i. e. an accommodation of ~2.51 dioptres at a wavelength of 534 nm, and correction of spherical aberration coefficient ranging from -0.8 to 0.67 waves. Frequency-switching technique was employed to increase the response speed and eliminate transient overshoots in aberration coefficients. The full-scale settling time of the adaptive modal corrector was measured to be ~4 s.
Wafer-level fabrication of arrays of glass lens doublets
Passilly, Nicolas; Perrin, Stéphane; Albero, Jorge; Krauter, Johann; Gaiffe, Olivier; Gauthier-Manuel, Ludovic; Froehly, Luc; Lullin, Justine; Bargiel, Sylwester; Osten, Wolfgang; Gorecki, Christophe
2016-04-01
Systems for imaging require to employ high quality optical components in order to dispose of optical aberrations and thus reach sufficient resolution. However, well-known methods to get rid of optical aberrations, such as aspherical profiles or diffractive corrections are not easy to apply to micro-optics. In particular, some of these methods rely on polymers which cannot be associated when such lenses are to be used in integrated devices requiring high temperature process for their further assembly and separation. Among the different approaches, the most common is the lens splitting that consists in dividing the focusing power between two or more optical components. In here, we propose to take advantage of a wafer-level technique, devoted to the generation of glass lenses, which involves thermal reflow in silicon cavities to generate lens doublets. After the convex lens sides are generated, grinding and polishing of both stack sides allow, on the first hand, to form the planar lens backside and, on the other hand, to open the silicon cavity. Nevertheless, silicon frames are then kept and thinned down to form well-controlled and auto-aligned spacers between the lenses. Subsequent accurate vertical assembly of the glass lens arrays is performed by anodic bonding. The latter ensures a high level of alignment both laterally and axially since no additional material is required. Thanks to polishing, the generated lens doublets are then as thin as several hundreds of microns and compatible with micro-opto-electro-systems (MOEMS) technologies since they are only made of glass and silicon. The generated optical module is then robust and provide improved optical performances. Indeed, theoretically, two stacked lenses with similar features and spherical profiles can be almost diffraction limited whereas a single lens characterized by the same numerical aperture than the doublet presents five times higher wavefront error. To demonstrate such assumption, we fabricated glass
TU-E-201-02: Eye Lens Dosimetry From CT Perfusion Studies
Zhang, D. [Toshiba America Medical Systems (United States)
2015-06-15
. These actions should be considered when they are consistent with the clinical task and patient anatomy. Learning Objectives: To become familiar with method of eye dose estimation for patient in specific situation of brain perfusion CT To become familiar with level of eye lens radiation doses in patients undergoing brain perfusion MDCT To understand methods for reducing eye lens dose to patient Jong Min Park, Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea Eye lens dosimetry in radiotherapy using contact lens-shaped applicator Dose calculation accuracy of commercial treatment planning systems is relatively low at shallow depths. Therefore, in-vivo measurements are often performed in the clinic to verify delivered doses to eye lens which are located at shallow depth. Current in-vivo dosimetry for eye lens during radiotherapy is generally performed with small in-vivo dosimeters on the surface of patient eyelid. Since this procedure potentially contains considerable uncertainty, a contact lens-shaped applicator made of acrylic (lens applicator) was developed for in-vivo measurements of eye lens dose during radiotherapy to reduce uncertainty. The lens applicator allows the insertion of commercially available metal oxide semiconductor field effect transistor (MOSFET) dosimeters. Computed tomography (CT) images of an anthropomorphic phantom with and without the lens applicator were acquired. A total of 20 VMAT plans were delivered to an anthropomorphic phantom and the doses with the lens applicator and the doses at the surface of the eyelid were measured using both micro and standard MOSFET dosimeters. The differences in measured dose at the surface of the eyelid from the calculated lens dose were acquired. The differences between the measured and the calculated doses at the lens applicator, as well as the differences between the measured and the calculated doses at the surface of the eyelid were acquired. The statistical significance of the
TU-E-201-00: Eye Lens Dosimetry for Patients and Staff
NONE
2015-06-15
. These actions should be considered when they are consistent with the clinical task and patient anatomy. Learning Objectives: To become familiar with method of eye dose estimation for patient in specific situation of brain perfusion CT To become familiar with level of eye lens radiation doses in patients undergoing brain perfusion MDCT To understand methods for reducing eye lens dose to patient Jong Min Park, Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea Eye lens dosimetry in radiotherapy using contact lens-shaped applicator Dose calculation accuracy of commercial treatment planning systems is relatively low at shallow depths. Therefore, in-vivo measurements are often performed in the clinic to verify delivered doses to eye lens which are located at shallow depth. Current in-vivo dosimetry for eye lens during radiotherapy is generally performed with small in-vivo dosimeters on the surface of patient eyelid. Since this procedure potentially contains considerable uncertainty, a contact lens-shaped applicator made of acrylic (lens applicator) was developed for in-vivo measurements of eye lens dose during radiotherapy to reduce uncertainty. The lens applicator allows the insertion of commercially available metal oxide semiconductor field effect transistor (MOSFET) dosimeters. Computed tomography (CT) images of an anthropomorphic phantom with and without the lens applicator were acquired. A total of 20 VMAT plans were delivered to an anthropomorphic phantom and the doses with the lens applicator and the doses at the surface of the eyelid were measured using both micro and standard MOSFET dosimeters. The differences in measured dose at the surface of the eyelid from the calculated lens dose were acquired. The differences between the measured and the calculated doses at the lens applicator, as well as the differences between the measured and the calculated doses at the surface of the eyelid were acquired. The statistical significance of the
Sion, N.
2016-09-15
Protecting the human body from the effects of ionizing radiation is essential to forestall stochastic effects and require placing limits on the effective dose. Dose limits on specific organs are also necessary to reduce the deterministic effects and tissue reactions. The standard for radiation protection was ISO 15382 (2002) which mainly dealt with beta radiation for nuclear power plant workers. Clearly an update is required to allow for new technology and the proliferative use of radiation in medical practices. There is a need for more explicit radiation monitoring to operators and staff. ICRP118 (International Commission on Radiological Protection), Ref. 1, evolved their recommendations to include eye lens doses as a follow on to their publication 103 and to focus on radiation exposures. It provides updated estimates of 'practical' threshold doses for tissue injury at the level of 1% incidence. This paper discusses the current status and the recommendation for a drastic reduction of the dose limit to the eye lens. (author)
Vorndran, Shelby D.; Wu, Yuechen; Ayala, Silvana; Kostuk, Raymond K.
2015-09-01
Concentrating and spectrum splitting photovoltaic (PV) modules have a limited acceptance angle and thus suffer from optical loss under off-axis illumination. This loss manifests itself as a substantial reduction in energy yield in locations where a significant portion of insulation is diffuse. In this work, a spectrum splitting PV system is designed to efficiently collect and convert light in a range of illumination conditions. The system uses a holographic lens to concentrate shortwavelength light onto a smaller, more expensive indium gallium phosphide (InGaP) PV cell. The high efficiency PV cell near the axis is surrounded with silicon (Si), a less expensive material that collects a broader portion of the solar spectrum. Under direct illumination, the device achieves increased conversion efficiency from spectrum splitting. Under diffuse illumination, the device collects light with efficiency comparable to a flat-panel Si module. Design of the holographic lens is discussed. Optical efficiency and power output of the module under a range of illumination conditions from direct to diffuse are simulated with non-sequential raytracing software. Using direct and diffuse Typical Metrological Year (TMY3) irradiance measurements, annual energy yield of the module is calculated for several installation sites. Energy yield of the spectrum splitting module is compared to that of a full flat-panel Si reference module.
Panoramic lens designed with transformation optics
Wang, Huaping; Deng, Yangyang; Zheng, Bin; Li, Rujiang; Jiang, Yuyu; Dehdashti, Shahram; Xu, Zhiwei; Chen, Hongsheng
2017-01-01
The panoramic lens is a special kind of lens, which is applied to observe full view. In this letter, we theoretically present a panoramic lens (PL) using transformation optics method. The lens is designed with inhomogeneous and anisotropic constitutive parameters, which has the ability to gather light from all directions and confine light within the visual angle of observer. Simulation results validate our theoretical design.
SimpLens: Interactive gravitational lensing simulator
Saha, Prasenjit; Williams, Liliya L. R.
2016-06-01
SimpLens illustrates some of the theoretical ideas important in gravitational lensing in an interactive way. After setting parameters for elliptical mass distribution and external mass, SimpLens displays the mass profile and source position, the lens potential and image locations, and indicate the image magnifications and contours of virtual light-travel time. A lens profile can be made shallower or steeper with little change in the image positions and with only total magnification affected.
L. R. Williams
2013-06-01
Full Text Available We have designed and characterized a new inlet and aerodynamic lens for the Aerodyne aerosol mass spectrometer (AMS that transmits particles between 80 nm and more than 3 μm in diameter. The design of the inlet and lens was optimized with computational fluid dynamics (CFD modeling of particle trajectories. Major changes include a redesigned critical orifice holder and valve assembly, addition of a relaxation chamber behind the critical orifice, and a higher lens operating pressure. The transmission efficiency of the new inlet and lens was characterized experimentally with size-selected particles. Experimental measurements are in good agreement with the calculated transmission efficiency.
In vivo human crystalline lens topography.
Ortiz, Sergio; Pérez-Merino, Pablo; Gambra, Enrique; de Castro, Alberto; Marcos, Susana
2012-10-01
Custom high-resolution high-speed anterior segment spectral domain optical coherence tomography (OCT) was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo. The system was provided with custom algorithms for denoising and segmentation of the images, as well as for fan (scanning) and optical (refraction) distortion correction, to provide fully quantitative images of the anterior and posterior crystalline lens surfaces. The method was tested on an artificial eye with known surfaces geometry and on a human lens in vitro, and demonstrated on three human lenses in vivo. Not correcting for distortion overestimated the anterior lens radius by 25% and the posterior lens radius by more than 65%. In vivo lens surfaces were fitted by biconicoids and Zernike polynomials after distortion correction. The anterior lens radii of curvature ranged from 10.27 to 14.14 mm, and the posterior lens radii of curvature ranged from 6.12 to 7.54 mm. Surface asphericities ranged from -0.04 to -1.96. The lens surfaces were well fitted by quadrics (with variation smaller than 2%, for 5-mm pupils), with low amounts of high order terms. Surface lens astigmatism was significant, with the anterior lens typically showing horizontal astigmatism ([Formula: see text] ranging from -11 to -1 µm) and the posterior lens showing vertical astigmatism ([Formula: see text] ranging from 6 to 10 µm).
21 CFR 886.3600 - Intraocular lens.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intraocular lens. 886.3600 Section 886.3600 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3600 Intraocular lens. (a) Identification. An intraocular lens is a device made of materials...
Poulsen, Bo
2016-01-01
Biolog og havforsker Johannes Schmidt regnes for at være Danmarks mest betydningsfulde havforsker gennem tiderne. Hans mange forskningsbaserede jordomsejlinger bragte ham til eksotiske egne og til opdagelsen af adskillige nye dyrearter. Dog blev særligt ålen og dens gydepladser et hovedfokus...
Poulsen, Bo
2016-01-01
Biolog og havforsker Johannes Schmidt regnes for at være Danmarks mest betydningsfulde havforsker gennem tiderne. Hans mange forskningsbaserede jordomsejlinger bragte ham til eksotiske egne og til opdagelsen af adskillige nye dyrearter. Dog blev særligt ålen og dens gydepladser et hovedfokus for ...
The Ultrawideband Leaky Lens Antenna
Bruni, S.; Neto, A.; Marliani, F.
2007-01-01
A novel directive and nondispersive antenna is presented: the ultrawideband (UWB) leaky lens. It is based on the broad band Cherenkov radiation occurring at a slot printed between different infinite homogeneous dielectrics. The first part of the paper presents the antenna concept and the UWB design.
Generation of terahertz hollow beams by a photonic quasi-crystal flat lens
Feng, Bo; Liu, Exian; Wang, Ziming; Cai, Weicheng; Liu, Hongfei; Wang, Shuo; Liang, Taiyuan; Xiao, Wei; Liu, Jianjun
2016-06-01
We have designed a decagonal photonic quasi-crystal (PQC) flat lens, which turns an incident terahertz (THz) plane wave into a hollow beam easily and flexibly. The features of the THz hollow beam can be controlled by varying the parameters of a point defect in the center of the lens, i.e., the PQC flat lens can be used as a flexible tool for THz optical captivity or optical tweezer. The results showing that an airy disk, whose mean beam width is similar to the incident wavelength and power-in-the-bucket (PIB) is more than 96%, can be generated in the far field.
Effect of oil on an electrowetting lenticular lens and related optical characteristics.
Shin, Dooseub; Kim, Junoh; Kim, Cheoljoong; Koo, Gyo Hyun; Sim, Jee Hoon; Lee, Junsik; Won, Yong Hyub
2017-03-01
While there are many ways to realize autostereoscopic 2D/3D switchable displays, the electrowetting lenticular lens is superior due to the high optical efficiency and short response time. In this paper, we propose a more stable electrowetting lenticular lens by controlling the quantity of oil. With a large amount of oil, the oil layer was broken and the lenticular lens was damaged at relatively low voltage. Therefore, controlling the amount of oil is crucial to obtain the required dioptric power with stability. We proposed a new structure to evenly adjust the volume of oil and the dioptric power was measured by varying the volume of oil. Furthermore, the optical characteristics were finally analyzed in the electrowetting lenticular lens array with a proper amount of oil.
Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Moustakas, Leonidas A.
2006-01-01
The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significantly higher than that of the SDSS target galaxy. The SLACS survey is optimized to detect bright early-type lens galaxies with faint lensed sources in order to increase the sample of known gravitational lenses suitable for detailed lensing, photometric, and dynamical modeling. In this paper, the first in a series on the current results of our HST Cycle 13 imaging survey, we present a catalog of 19 newly discovered gravitational lenses, along with nine other observed candidate systems that are either possible lenses, nonlenses, or nondetections. The survey efficiency is thus >=68%. We also present Gemini 8 m and Magellan 6.5 m integral-field spectroscopic data for nine of the SLACS targets, which further support the lensing interpretation. A new method for the effective subtraction of foreground galaxy images to reveal faint background features is presented. We show that the SLACS lens galaxies have colors and ellipticities typical of the spectroscopic parent sample from which they are drawn (SDSS luminous red galaxies and quiescent MAIN sample galaxies), but are somewhat brighter and more centrally concentrated. Several explanations for the latter bias are suggested. The SLACS survey provides the first statistically significant and homogeneously selected sample of bright early-type lens galaxies, furnishing a powerful probe of the structure of early-type galaxies within the half-light radius. The high confirmation rate of lenses in the SLACS survey suggests consideration of spectroscopic lens discovery as an explicit science goal of future spectroscopic galaxy surveys.
Multifocal contact lens myopia control.
Walline, Jeffrey J; Greiner, Katie L; McVey, M Elizabeth; Jones-Jordan, Lisa A
2013-11-01
Previous studies on soft multifocal contact lens myopia control published in the peer-reviewed literature reported findings of noncommercial contact lenses worn for 1 year or less. This study sought to determine the progression of myopia and axial elongation of children fitted with commercially available distance center soft multifocal contact lenses for 2 years. Eight- to eleven-year-old children with -1.00 D to -6.00 D spherical component and less than 1.00 D astigmatism were fitted with soft multifocal contact lenses with a +2.00 D add (Proclear Multifocal "D"; CooperVision, Fairport, NY). They were age- and gender-matched to participants from a previous study who were fitted with single-vision contact lenses (1 Day Acuvue; Vistakon, Jacksonville, FL). A-scan ultrasound and cycloplegic autorefraction were performed at baseline, after 1 year, and after 2 years. Multilevel modeling was used to compare the rate of change of myopia and axial length between single-vision and soft multifocal contact lens wearers. Forty participants were fitted with soft multifocal contact lenses, and 13 did not contribute complete data (5 contributed 1 year of data). The adjusted mean ± standard error spherical equivalent progression of myopia at 2 years was -1.03 ± 0.06 D for the single-vision contact lens wearers and -0.51 ± 0.06 for the soft multifocal contact lens wearers (p < 0.0001). The adjusted mean axial elongation was 0.41 ± 0.03 and 0.29 ± 0.03 for the single-vision and soft multifocal contact lens wearers, respectively (p < 0.0016). Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the 2-year treatment period compared to a historical control group. Results from this and other investigations indicate a need for a long-term randomized clinical trial to investigate the potential for soft multifocal contact lens myopia control.
Bringing the 'perfect lens' into focus by near-perfect compensation of losses without gain media
Adams, Wyatt; Zhang, Xu; Güney, Durdu Ö
2016-01-01
In this paper, the optical properties and imaging performance of a non-ideal Pendry's negative index flat lens with a practical value for loss are studied. Analytical calculations of the optical properties of the lens are performed, and those results are used to further study the lens and corresponding imaging system numerically. The plasmon injection scheme for loss compensation in negative index metamaterials is applied to the results from the imaging system, resulting in a perfect reconstruction of a previously unresolved image that demonstrates sub-diffraction-limit resolution.
Lens stem cells may reside outside the lens capsule: an hypothesis
Meyer Rita A
2007-06-01
Full Text Available Abstract In this paper, we consider the ocular lens in the context of contemporary developments in biological ideas. We attempt to reconcile lens biology with stem cell concepts and a dearth of lens tumors. Historically, the lens has been viewed as a closed system, in which cells at the periphery of the lens epithelium differentiate into fiber cells. Theoretical considerations led us to question whether the intracapsular lens is indeed self-contained. Since stem cells generate tumors and the lens does not naturally develop tumors, we reasoned that lens stem cells may not be present within the capsule. We hypothesize that lens stem cells reside outside the lens capsule, in the nearby ciliary body. Our ideas challenge the existing lens biology paradigm. We begin our discussion with lens background information, in order to describe our lens stem cell hypothesis in the context of published data. Then we present the ciliary body as a possible source for lens stem cells, and conclude by comparing the ocular lens with the corneal epithelium.
Dose conversion coefficients for neutron exposure to the lens of the human eye
Manger, Ryan P [ORNL; Bellamy, Michael B [ORNL; Eckerman, Keith F [ORNL
2011-01-01
Dose conversion coefficients for the lens of the human eye have been calculated for neutron exposure at energies from 1 x 10{sup -9} to 20 MeV and several standard orientations: anterior-to-posterior, rotational and right lateral. MCNPX version 2.6.0, a Monte Carlo-based particle transport package, was used to determine the energy deposited in the lens of the eye. The human eyeball model was updated by partitioning the lens into sensitive and insensitive volumes as the anterior portion (sensitive volume) of the lens being more radiosensitive and prone to cataract formation. The updated eye model was used with the adult UF-ORNL mathematical phantom in the MCNPX transport calculations.
Large scale water lens for solar concentration.
Mondol, A S; Vogel, B; Bastian, G
2015-06-01
Properties of large scale water lenses for solar concentration were investigated. These lenses were built from readily available materials, normal tap water and hyper-elastic linear low density polyethylene foil. Exposed to sunlight, the focal lengths and light intensities in the focal spot were measured and calculated. Their optical properties were modeled with a raytracing software based on the lens shape. We have achieved a good match of experimental and theoretical data by considering wavelength dependent concentration factor, absorption and focal length. The change in light concentration as a function of water volume was examined via the resulting load on the foil and the corresponding change of shape. The latter was extracted from images and modeled by a finite element simulation.
Solar lens mission concept for interstellar exploration
Brashears, Travis; Lubin, Philip; Turyshev, Slava; Shao, Michael; Zhang, Qicheng
2015-09-01
The long standing approach to space travel has been to incorporate massive on-board electronics, probes and propellants to achieve space exploration. This approach has led to many great achievements in science, but will never help to explore the interstellar medium. Fortunately, a paradigm shift is upon us in how a spacecraft is constructed and propelled. This paper describes a mission concept to get to our Sun's Gravity Lens at 550AU in less than 10 years. It will be done by using DE-STAR, a scalable solar-powered phased-array laser in Earth Orbit, as a directed energy photon drive of low-mass wafersats. [1] [2] [3] [4] [5] With recent technologies a complete mission can be placed on a wafer including, power from an embedded radio nuclear thermal generator (RTG), PV, laser communications, imaging, photon thrusters for attitude control and other sensors. As one example, a futuristic 200 MW laser array consisting of 1 - 10 kw meter scale sub elements with a 100m baseline can propel a 10 gram wafer scale spacecraft with a 3m laser sail to 60AU/Year. Directed energy propulsion of low-mass spacecraft gives us an opportunity to capture images of Alpha Centauri and its planets, detailed imaging of the cosmic microwave background, set up interstellar communications by using gravity lenses around nearby stars to boost signals from interstellar probes, and much more. This system offers a very large range of missions allowing hundreds of wafer scale payload launches per day to reach this cosmological data reservoir. Directed Energy Propulsion is the only current technology that can provide a near-term path to utilize our Sun's Gravity Lens.
Study on the beam shaping of high-power laser diode bars
Wei Huang(黄伟); Xiaodong Zeng(曾晓东); Yuying An(安毓英)
2003-01-01
Based on the Collins form, the intensity distribution of the resulting beam is derived when Gaussian beamsof a high-power laser diode bar pass through a paraxial optical system. Then flattop beam profiles areobtained by a concave cylindrical lens, and the propagation properties are discussed in detail, such as thepeak-intensity axis inclined at an angle γi. In addition, an expression to calculate beam angular width ispresented.
The Design of Lens Imaging System by Means of Fractional Fourier Transform
CHEN Jiannong; XU Qiang; D.R.Selviah
2002-01-01
The relation between the 2nd fractional Fourier transform and the imaging process of an optical system is discussed. By changing the coordinate scales of the input plane in respect to the magnification of the optical imaging system, the fractional Fourier transform can be a powerful tool in designing specific imaging system. The Gaussian imaging formula of single lens is obtained by using the tool. Finally the procedures are generalized for designing a double-lens imaging system through an example.
First-order method of zoom lens design by means of generalized parameters.
Khorokhorov, Alexei M; Piskunov, Dmitry E; Shirankov, Alexander F
2016-08-01
A method of paraxial zoom lens design is proposed that makes it possible to determine the optical powers and component movements of a zoom lens with the required zoom ratio. The method is based on the theory of generalized parameters, which can be used to analyze a zoom system by varying only one parameter. All possible zoom lenses with two movable components are considered for an object at infinity.
Modern lens antennas for communications engineering
Thornton, John
2012-01-01
The aim of this book is to present the modern design principles and analysis of lens antennas. It gives graduates and RF/Microwave professionals the design insights in order to make full use of lens antennas. Why do we want to write a book in lens antennas? Because this topic has not been thoroughly publicized, its importance is underestimated. As antennas play a key role in communication systems, recent development in wireless communications would indeed benefit from the characteristics of lens antennas: low profile, and low cost etc. The major advantages of lens antennas are na
Comparison of two optical biometers in intraocular lens power calculation%两种光学生物测量仪测算人工晶状体度数的比较研究
生晖; 卢奕
2012-01-01
目的 比较光学低相干反射仪LENSTAR和光学相干生物测量仪IOL Master测算人工晶状体(IOL)度数的差异,分析两者的精确性和一致性.方法 72例(122眼)自内障患者术前分别用LENSTAR和IOL Master两种光学生物测量仪测量眼轴长度(AL)、角膜屈光度(K1和K2)和前房深度(ACD),并分别应用SRK Ⅱ、SRK/T、Hoffer Q、Holladay和Haigis公式计算拟植入AcrySof SA60AT IOL的度数,术后目标屈光度为正视.结果 两种测量仪所得参数:AL差异为(0.02±0.10)mm,ACD差异为(-0.02±0.17)mm,差异均无统计学意义(P>0.05);K1、K2和(K1+K2)/2差异分别为(-0.05±0.21)D、(-0.12±0.20)D和(-0.08±0.14)D,差异有统计学意义(P<0.05).两种测量仪测量的参数AL、K1、K2和ACD的Pearson r值分别是0.999、0.991、0.992和0.927,具有良好的相关性.应用5种IOL度数计算公式得出的IOL度数在两种测量仪之间,差异无统计学意义,有良好的一致性.结论 LENSTAR和IOL Master测量仪在测量结果和计算IOL度数方面有良好的相关性和一致性,均可用于白内障手术前精确的IOL度数测算.
Broadband Wide Angle Lens Implemented with Dielectric Metamaterials
Anthony Starr; Nathan Landy; Vinh Nguyen; Tim Perram; Nathan Kundtz; John Hunt; Smith, David R.
2011-01-01
The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide fi...
Yang, M; Virshup, G; Clayton, J; Zhu, X R; Mohan, R; Dong, L
2010-03-07
We discovered an empirical relationship between the logarithm of mean excitation energy (ln Im) and the effective atomic number (EAN) of human tissues, which allows for computing patient-specific proton stopping power ratios (SPRs) using dual-energy CT (DECT) imaging. The accuracy of the DECT method was evaluated for 'standard' human tissues as well as their variance. The DECT method was compared to the existing standard clinical practice-a procedure introduced by Schneider et al at the Paul Scherrer Institute (the stoichiometric calibration method). In this simulation study, SPRs were derived from calculated CT numbers of known material compositions, rather than from measurement. For standard human tissues, both methods achieved good accuracy with the root-mean-square (RMS) error well below 1%. For human tissues with small perturbations from standard human tissue compositions, the DECT method was shown to be less sensitive than the stoichiometric calibration method. The RMS error remained below 1% for most cases using the DECT method, which implies that the DECT method might be more suitable for measuring patient-specific tissue compositions to improve the accuracy of treatment planning for charged particle therapy. In this study, the effects of CT imaging artifacts due to the beam hardening effect, scatter, noise, patient movement, etc were not analyzed. The true potential of the DECT method achieved in theoretical conditions may not be fully achievable in clinical settings. Further research and development may be needed to take advantage of the DECT method to characterize individual human tissues.
Conjunctival impression cytology in contact lens wearers.
Simon Priya
2002-01-01
Full Text Available PURPOSE: To evaluate the cytological changes in conjunctiva following regular contact lens wear and to determine the correlation, if any, between severity of cytological alteration and symptoms related to contact lens wear. METHODS: One hundred eyes (50 normal asymptomatic subjects who served as a control group were studied by conjunctival impression cytology (CIC. These subjects were fitted with rigid gas permeable (RGP or soft contact lenses and were followed up at the end of 3 and 6 months. At each follow-up visit the CIC was repeated. A filter paper with the impression specimen was stained with periodic acid schiff (PAS and haematoxylin stain to study goblet cell loss. Papanicolaou stain was done to study squamous metaplasia. The cytological changes were graded using the system described by Natadisastra et al. RESULTS: Severity of cytological changes increased with the duration of contact lens wear (P = 0.00001. At the end of 6 months, 60% of symptomatic eyes wearing soft contact lens and RGP lens showed abnormal CIC changes. None of the asymptomatic RGP contact lens wearing eyes showed abnormal CIC changes whereas 33.4% of the asymptomatic soft contact lens wearing eyes showed abnormal CIC changes (P = 0.033. Epithelial changes occurred within 3-6 months of contact lens fitting. CONCLUSION: Severity of cytological changes increased with duration of lens wear (P = 0.00001. Prevalence and severity of cytological alteration is more in symptomatic contact lens wearers. Soft contact lens wearers although asymptomatic showed severe CIC changes.
The effect of gain saturation in a gain compensated perfect lens
Andresen, Marte P Hatlo; Haakestad, Magnus W; Krogstad, Harald E; Skaar, Johannes
2010-01-01
The transmission of evanescent waves in a gain-compensated perfect lens is discussed. In particular, the impact of gain saturation is included in the analysis, and a method for calculating the fields of such nonlinear systems is developed. Gain compensation clearly improves the resolution; however, a number of nonideal effects arise as a result of gain saturation. The resolution associated with the lens is strongly dependent on the saturation constant of the active medium.
Electro-optically actuated liquid-lens zoom
Pütsch, O.; Loosen, P.
2012-06-01
Progressive miniaturization and mass market orientation denote a challenge to the design of dynamic optical systems such as zoom-lenses. Two working principles can be identified: mechanical actuation and application of active optical components. Mechanical actuation changes the focal length of a zoom-lens system by varying the axial positions of optical elements. These systems are limited in speed and often require complex coupled movements. However, well established optical design approaches can be applied. In contrast, active optical components change their optical properties by varying their physical structure by means of applying external electric signals. An example are liquidlenses which vary their curvatures to change the refractive power. Zoom-lenses benefit from active optical components in two ways: first, no moveable structures are required and second, fast response characteristics can be realized. The precommercial development of zoom-lenses demands simplified and cost-effective system designs. However the number of efficient optical designs for electro-optically actuated zoom-lenses is limited. In this paper, the systematic development of an electro-optically actuated zoom-lens will be discussed. The application of aberration polynomials enables a better comprehension of the primary monochromatic aberrations at the lens elements during a change in magnification. This enables an enhanced synthesis of the system behavior and leads to a simplified zoom-lens design with no moving elements. The change of focal length is achieved only by varying curvatures of targeted integrated electro-optically actuated lenses.
任琦梅; 姜建
2014-01-01
大功率H桥逆变器中广泛采用IGBT作为开关器件，传统的IGBT开关损耗计算是基于供应商提供的开关能量曲线，而该曲线上所提供的开关能量与逆变器实际运行时的数据有较大出入。为此，提出了一套完整的大功率H桥逆变器的损耗分析与精确计算方法。逆变器损耗主要包括IGBT损耗和电解电容损耗，而IGBT损耗又包括导通损耗、开通损耗、关断损耗和反向恢复损耗。给出了各类损耗的定量计算方法，并且采用了双脉冲测试方法获得实际开关能量曲线，因此计算结果更加精确。搭建了一台3.45kVA的实验样机，1kHz开关频率下满载运行时，计算损耗为218W，实测损耗为210W。实验结果验证了所提出的分析与计算方法的准确性。%IGBT is widely used in high power H-bridge inverter. Traditional IGBT switching loss calculation method is mainly based on the switching energy curves provided by the suppliers, which is quite different from the real switching energy. Therefore, a refined calculation method of high power H-bridge inverter has been proposed in this paper. The power losses of inverter always include IGBT power loss and capacitor power loss, while the IGBT power losses always include conduction power loss, turn-on power loss, turn-off power loss and reverse recovery power loss. The quantitative calculation methods for different power losses are presented and the real switching energy curves are obtained using double pulse test way, which will provide a more precise calculation result. Finally, a 3.45kVA prototype has been built, and the calculated power loss is 218W with the measured power loss as 210W under 1kHz switching frequency at full load. The experimental results verify the accuracy of the proposed method.
Chang, G. S.; Lillo, M. A.
2009-08-01
-Z mini-plate fuel model was developed. The Y-Z model divides each fuel plate into 30 equal intervals in both the Y and Z directions. The MCNP-calculated results and the detailed Y-Z fission power mapping were used to help design the AFIP fuel test assembly to demonstrate that the AFIP test assembly thermal-hydraulic limits will not exceed the ATR safety limits.
Study on Titanium Nitride Film Modified for Intraocular Lens
无
2009-01-01
Objective:To study the characteristics of the intraocular lens using ion beam sputtering depositing titanium nitride thin film on the intraocular lens(IOLs).Methods:To deposite titanium nitride thin film on the top of intraocular lens by ion beam sputtering depositing.We analyzed the surface morphology of intraocular lens through SEM and AFM.We detected intraocular lens resolution through the measurement of intraocular lens.Biocompatibility of intraocular lens is preliminary evaluated in this test.Results:T...
Rushton, Christopher E; Tate, James E; Shepherd, Simon P; Carslaw, David C
2017-03-13
Emissions of NOX by vehicles in real driving environments are only partially understood. This has been brought to the attention of the world with recent revelations of the cheating of the type approval tests exposed in the dieselgate scandal. Remote sensing devices offer investigators an opportunity to directly measure in-situ real driving emissions of tens of thousands of vehicles. The availability of remote sensing NO2 measurements are not as widely available as would be desirable. The aim of this study is to improve the ability of investigators to estimate the NO2 emissions and to improve the confidence of the total NOX results calculated from standard RSD measurements. The accuracy of the RSD speed and acceleration module was also validated using state-of-the-art onboard GPS tracking. Two RSDs used in roadside vehicle emissions surveys were tested side by side under off carriageway conditions away from transient pollution sources to ascertain the consistency of their measurements. The speed correlation was consistent across the range of measurements at 95% confidence and the acceleration correlation was consistent at 95% confidence intervals for all but the most extreme acceleration cases. VSP was consistent at 95% confidence across all measurements except for VSP ≥ 15kW t(-1) which show a small underestimate. The controlled distribution gas nitric oxide measurements follow a normal distribution with 2σ equal to 18.9% of the mean compared to 15% that was observed during factory calibration indicative of additional error introduced into the system. Systematic errors of +84ppm were observed but within the tolerance of the control gas. Inter-instrument correlation was performed with the relationship between the FEAT and the RSD4600 being linear with a gradient of 0.93 and an R(2) of 0.85 indicating good correlation. A new method to calculate NOX emissions using fractional NO2 combined with NO measurements made by the RSD4600 was constructed, validated and shown
Lens Coupled Quantum Cascade Laser
Hu, Qing (Inventor); Lee, Alan Wei Min (Inventor)
2013-01-01
Terahertz quantum cascade (QC) devices are disclosed that can operate, e.g., in a range of about 1 THz to about 10 THz. In some embodiments, QC lasers are disclosed in which an optical element (e.g., a lens) is coupled to an output facet of the laser's active region to enhance coupling of the lasing radiation from the active region to an external environment. In other embodiments, terahertz amplifier and tunable terahertz QC lasers are disclosed.
Fresnel Lens with Embedded Vortices
Sunil Vyas
2012-01-01
Full Text Available Vortices of different charges are embedded in a wavefront that has quadratic phase variation, and the intensity distribution near the focal plane is studied. This method may be useful in realizing complicated beam profiles. We have experimentally demonstrated the generation of vortex arrays having integer as well as fractional topological charges that produce different intensity profiles at the focal plane. The phase variation realized on a spatial light modulator (SLM acts as a Fresnel lens with embedded vortices.
Vianna, E.A.L. [Centrais Eletricas do Norte (ELETRONORTE), Porto Velho, RO (Brazil)], E-mail: elainelimavianna@yahoo.com.br; Lambert-Torres, G.; Silva, L.E.B. da [Universidade Federal de Itajuba (UNIFEI), MG (Brazil)], Emails: germanoltorres@gmail.com, leborges@unifei.edu.br; Rissino, S.; Silva, M.F. da [Universidade Federal de Rondonia (UFRO), Porto Velho, RO (Brazil)], Emails: srissino@gmail.com, felipe@unir.br
2009-07-01
Disturbances recorded in a electric power system compromise the quality and continuity energy supply and are measured by means of performance indicators. This article defines the attributes that contribute to increased the severity of disturbances recorded in an Electrical Power Transmission and proposes a methodology for calculating the degree of impact caused each of them. The proposed methodology allows quantification of the impact caused by a disturbance, and its comparison with other disturbance, in one system or distinct systems.
Contact lens wear is intrinsically inflammatory.
Efron, Nathan
2017-01-01
Eye-care practitioners typically associate ocular inflammation during contact lens wear with serious complications such as microbial keratitis; however, more subtle mechanisms may be at play. This paper tests the notion that contact lens wear is intrinsically inflammatory by exploring whether uncomplicated contact lens wear meets the classical, clinical definition of inflammation - rubor (redness), calor (heat), tumor (swelling), dolor (pain) and functio laesa (loss of function) - as well as the contemporary, sub-clinical definition of inflammation (cellular and biochemical reactions). It is demonstrated that all of these clinical and sub-clinical criteria are met with hydrogel lens wear and most are met with silicone hydrogel lens wear, indicating that uncomplicated contact lens wear is intrinsically inflammatory. Consideration of both traditional and contemporary thinking about the role of inflammation in the human body leads to the perhaps surprising conclusion that the chronic, low grade, sub-clinical inflammatory status of the anterior eye during contact lens wear, which may be termed 'para-inflammation', is a positive, protective phenomenon, whereby up-regulation of the immune system, in a non-damaging way, maintains the eye in a state of 'heightened alert', ready to ward off any extrinsic noxious challenge. Characterisation of this inflammatory status may lead to the development of lens engineering or pharmacological strategies to modulate contact lens-induced inflammation, so as to render lens wear more safe and comfortable. © 2016 Optometry Australia.
Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter
Neisius, Andreas; Smith, Nathan B.; Sankin, Georgy; Kuntz, Nicholas John; Madden, John Francis; Fovargue, Daniel E.; Mitran, Sorin; Lipkin, Michael Eric; Simmons, Walter Neal; Preminger, Glenn M.; Zhong, Pei
2014-01-01
The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The −6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters. PMID:24639497
An exploration into diffusion tensor imaging in the bovine ocular lens
Ehsan eVaghefi
2013-03-01
Full Text Available We describe our development of the diffusion tensor imaging modality for the bovine ocular lens. Diffusion gradients were added to a spin-echo pulse sequence and the relevant parameters of the sequence were refined to achieve good diffusion weighting in the lens tissue, which demonstrated heterogeneous regions of diffusive signal attenuation. Decay curves for b-value (loosely summarizes the strength of diffusion weighting and TE (determines the amount of MRI-obtained signal were used to estimate apparent diffusion coefficients (ADC and T2 in different lens regions. The ADCs varied by over an order of magnitude and revealed diffusive anisotropy in the lens. Up to 30 diffusion gradient directions, and 8 signal acquisition averages, were applied to lenses in culture in order to improve maps of diffusion tensor eigenvalues, equivalent to ADC, across the lens. From these maps, fractional anisotropy maps were calculated and compared to known spatial distributions of anisotropic molecular fluxes in the lens. This comparison suggested new hypotheses and experiments to quantitatively assess models of circulation in the avascular lens.
Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter.
Neisius, Andreas; Smith, Nathan B; Sankin, Georgy; Kuntz, Nicholas John; Madden, John Francis; Fovargue, Daniel E; Mitran, Sorin; Lipkin, Michael Eric; Simmons, Walter Neal; Preminger, Glenn M; Zhong, Pei
2014-04-01
The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters.
Focal length measurement of a varifocal liquid lens with capacitance detection
Noda, Kentaro; Binh-Khiem, Nguyen; Takei, Yusuke; Takahata, Tomoyuki; Matsumoto, Kiyoshi; Shimoyama, Isao
2014-04-01
This paper reports on a detailed deformation model of varifocal liquid lenses fabricated by Parylene-on-liquid-deposition (POLD), which can be applied to measure and adjust the focal length of such lenses without using extra sensors or sensing mechanisms. The lens was fabricated by encapsulating a liquid between a transparent electrode and a polymer film that was covered with a metal electrode. When voltage is applied to the two electrodes, the lens deforms due to the electrostatic force, and its focal length and the capacitance between the two electrodes change simultaneously. This characteristic enables the focal length of the lens to be adjusted and detected by measuring the capacitance change. The focal length of the fabricated varifocal liquid lens changed from 153.6 to 82.6 mm by applying 150-V. The focal length change of the liquid lens was calculated from the change in its capacitance. Finally, to confirm the efficiency of this varifocal liquid lens, we fabricated a confocal distance sensor using the lens for laser scanning and demonstrated that this system can be used to measure distances of 94-140 mm with an average error of 0.83 mm and a standard deviation of 0.77 mm.
Lens magnification by CL0024+1654 in the U and R band
Dye, S.; Taylor, A. N.; Greve, T. R.; Rögnvaldsson, Ö. E.; van Kampen, E.; Jakobsson, P.; Sigmundsson, V. S.; Gudmundsson, E. H.; Hjorth, J.
2002-04-01
We estimate the total mass distribution of the galaxy cluster CL0024+1654 from the measured source depletion due to lens magnification in the R band. Within a radius of 0.54 h-1 Mpc, a total projected mass of (8.1 +/- 3.2)x 1014 h-1 Msun (EdS) is measured. The 1sigma error here includes shot noise, source clustering, uncertainty in background count normalisation and contamination from cluster and foreground galaxies. This corresponds to a mass-to-light ratio of M/LB=470+/-180. We compute the luminosity function of CL0024+1654 in order to estimate contamination of the background source counts from cluster galaxies. Three different magnification-based reconstruction methods are employed: 1) an estimator method using a local calculation of lens shear; 2) a non-local, self-consistent method applicable to axi-symmetric mass distributions; 3) a non-local, self-consistent method for derivation of 2D mass maps. We have modified the standard single power-law slope number count theory to incorporate a break and applied this to our observations. Fitting analytical magnification profiles of different cluster models to the observed number counts, we find that CL0024+1654 is best described either by a NFW model with scale radius rs= 334+/-191 h-1 kpc and normalisation kappas = 0.23+/-0.08 or a power-law profile with slope xi=0.61+/-0.11, central surface mass density kappa0 =1.52+/-0.20 and assuming a core radius of rcore=35 h-1 kpc. The NFW model predicts that the cumulative projected mass contained within a radius R scales as M( 0.15 up to UABconfidence.
Elasticity of the eye's crystalline lens: A Brillouin light scattering study.
Bailey, S.; Gump, J.; Sooryakumar, R.; Jayaprakash, C.; Venkiteshwar, M. S.; Bullimore, M.; Twa, M.
2009-03-01
Focusing the eye on a near object results in an increase in its optical power brought about by contraction of the ciliary muscles and an increase in the lens surface curvature. Distant vision occurs when the muscular force flattens the lens. Central to the ability of the lens to alter shape are its mechanical properties. Thus, given that hardening of the lens would impede deformation and reduce its ability to undergo the changes required for accommodation, a noninvasive approach to measure the elastic properties of the lens is valuable. We present results of Brillouin scattering from bovine and human lenses (from the organ donor program at The Ohio State University) that measure their high frequency acoustic response. These measurements are conducted with a few milli-watts of laser power and, in the case of bovine lenses, from entire intact eye globes, allow the stiffness of the lens to be mapped across its cross-section. The results will be compared to values of the shear- and bulk-moduli determined from other techniques and the implications of differences in these moduli discussed.
Negative refractive perfect lens vs Spherical geodesic lens. Perfect Imaging comparative analysis
Gonzalez, Juan C; Minano, Juan C; Grabovickic, Dejan
2012-01-01
Negative Refractive Lens (NRL) has shown that an optical system can produce images with details below the classic Abbe diffraction limit. This optical system transmits the electric field, emitted by the object surface, towards the image surface producing the same field distribution in both surfaces. In particular, a Dirac delta electric field in the object surface is focused without diffraction limit to the Dirac delta electric field in the image surface. The Maxwell Fish Eye lens (MFE) and the Spherical Geodesic Waveguide (SGW) have been claimed to break the diffraction limit using positive refraction with a different meaning. In these cases, it has been considered the power transmission from a point source to a point receptor, which falls drastically when the receptor is displaced from the focus by a distance much smaller than the wavelength. Although these systems can detect displacements up to Wavelength/500, they cannot be compared to the NRL, since the concept of the object and image surface is not esta...
Sustainability through the Lens of Environmental Sociology: An Introduction
Md Saidul Islam
2017-03-01
Full Text Available Our planet is undergoing radical environmental and social changes. Sustainability has now been put into question by, for example, our consumption patterns, loss of biodiversity, depletion of resources, and exploitative power relations. With apparent ecological and social limits to globalization and development, current levels of consumption are known to be unsustainable, inequitable, and inaccessible to the majority of humans. Understanding and achieving sustainability is a crucial matter at a time when our planet is in peril—environmentally, economically, socially, and politically. Since its official inception in the 1970s, environmental sociology has provided a powerful lens to understanding the challenges, possibilities, and modes of sustainability. This editorial, accompanying the Special Issue on “sustainability through the Lens of Environmental Sociology”, first highlights the evolution of environmental sociology as a distinct field of inquiry, focusing on how it addresses the environmental challenges of our time. It then adumbrates the rich theoretical traditions of environmental sociology, and finally examines sustainability through the lens of environmental sociology, referring to various case studies and empirical analyses.
Luneburg lens with extended flat focal surface for electronic scan applications.
Li, Ying; Zhu, Qi
2016-04-01
Luneburg lens with flat focal surface has been developed to work together with planar antenna feeds for beam steering applications. According to our analysis of the conventional flattened Luneburg lens, it cannot accommodate enough feeding elements which can cover its whole scan range with half power beamwidths (HPBWs). In this paper, a novel Luneburg lens with extended flat focal surface is proposed based on the theory of Quasi-Conformal Transformation Optics (QCTO), with its beam steering features reserved. To demonstrate this design, a three-dimensional (3D) prototype of this novel extend-flattened Luneburg lens working at Ku band is fabricated based on 3D printing techniques, whose flat focal surface is attached to a 9-element microstrip antenna array to achieve different scan angles. Our measured results show that, with different antenna elements being fed, the HPBWs can cover the whole scan range.
Evolution of a pre and post lens tear film with a contact lens
Gerhart, Matthew; Anderson, Daniel
2012-11-01
The work is the development, implementation, and analysis of a two-dimensional tear film model including a porous contact lens. The geometry of the problem is: a pre-lens layer that is a thin tear film between the outside air and contact lens, a contact lens that is a rigid but movable porous substrate, and a post-lens layer that is a thin film layer between the contact lens and the cornea. We are looking at short and long term behavior of the evolution of the thin film in the pre-lens layer coupled with the porous layer and the thin squeeze film in the post-lens layer. We model the different behaviors that arise as the Darcy number, evaporation effects, and boundary flux conditions change.
Lateral shear interferometry with holo shear lens
Joenathan, C.; Mohanty, R. K.; Sirohi, R. S.
1984-12-01
A simple method for obtaining lateral shear using holo shear lenses (HSL) has been discussed. This simple device which produces lateral shears in the orthogonal directions has been used for lens testing. The holo shear lens is placed at or near the focus of the lens to be tested. It has also been shown that HSL can be used in speckle shear interferometry as it performs both the functions of shearing and imaging.
An inverse and analytic lens design method
Lu, Yang; Lakshminarayanan, Vasudevan
2016-01-01
Traditional lens design is a numerical and forward process based on ray tracing and aberration theory. This method has limitations because the initial configuration of the lens has to be specified and the aberrations of the lenses have to considered. This paper is an initial attempt to investigate an analytic and inverse lens design method, called Lagrange, to overcome these barriers. Lagrange method tries to build differential equations in terms of the system parameters and the system input ...
Bae, Jae Hyun; Song, Sung Jin; Kim, Hak Joon [School of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kim, Ki Bok [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)
2015-04-15
Traditional moxibustion therapy can cause severe pain and leave scarring burns at the moxibustion site as it relies on the practitioner's subjective and qualitative treatment. Recently, ultrasound therapy has received attention as an alternative to moxibustion therapy owing to its objectiveness and quantitative nature. However, in order to convert ultrasound energy into heat energy, there is a need to precisely understand the ultrasound-focusing characteristics of the acoustic lens. Therefore, in this study, an FEM simulation was performed for acoustic lenses with different geometries a concave lens and zone lens as the geometry critically influences ultrasound focusing. The acoustic pressure field, amplitude, and focal point were also calculated. Furthermore, the performance of the fabricated acoustic lens was verified by a sound pressure measurement experiment.
Evaluation of intraocular lens implant location in the eyeball basing on the Purkinje images
Jóźwik, A.; Siedlecki, D.; Zajac, M.
2012-01-01
Intraocular lens (IOL) is an artificial implant substituting natural crystalline lens which is non-transparent due to cataract. Incorrect location of the IOL in the eyeball (e.g. its shift or tilt) causes significant deterioration of patient's vision. The analysis of Purkinje images (i.e. reflections from successive refracting surfaces in the eye) enables to determine the real IOL location and thus helps in evaluating the retinal image quality. The experimental setup for Purkinje images recording consists of illuminator, composed of a number of infrared LEDs, telecentric lens and detector (CCD camera). Analysis of mutual position of particular reflections enables to evaluate the lens location in respect to the corneal axis. The actual measurements are realized on artificial eye model, what allows to estimate the precision of the algorithm applied in the calculations. In the future the experimental set-up will be adapted to measure the eyes of real patients.
Noncontact optical measurement of lens capsule thickness ex vivo
Ziebarth, Noel M.; Manns, Fabrice; Uhlhorn, Stephen; Parel, Jean-Marie
2004-07-01
Purpose: To design a non-contact optical system to measure lens capsule thickness in cadaver eyes. Methods: The optical system uses a 670nm laser beam delivered to a single-mode fiber coupler. The output of the fiber coupler is focused onto the tissue using an aspheric lens (NA=0.68) mounted on a motorized translation stage. Light reflected from the sample is collected by the fiber coupler and sent to a silicon photodiode connected to a power meter. Peaks in the power signal are detected when the focal point of the aspheric lens coincides with the capsule boundaries. The capsule thickness is proportional to the distance between successive peaks. Anterior and posterior lens capsule thickness measurements were performed on 13 human, 10 monkey, and 34 New Zealand white rabbit lenses. The cadaver eyes were prepared for optical measurements by bonding a PMMA ring on the sclera. The posterior pole was sectioned, excess vitreous was removed, and the eye was placed on a Teflon slide. The cornea and iris were then sectioned. After the experiments, the lenses were excised, placed in 10% buffered formalin, and prepared for histology. Results: Central anterior lens capsule thickness was 9.4+/-2.9μm (human), 11.2+/-6.6μm (monkey), and 10.3+/-3.6μm (rabbit) optically and 14.9+/-1.6μm (human), 17.7+/-4.9μm (monkey), and 12.6+/-2.3μm (rabbit) histologically. The values for the central posterior capsule were 9.4+/-2.9μm (human), 6.6+/-2.5μm (monkey), and 7.9+/-2.3μm (rabbit) optically and 4.6+/-1.4μm (human), 4.5+/-1.2μm (monkey), and 5.7+/-1.7μm (rabbit) histologically. Conclusions: This study demonstrates that a non-contact optical system can successfully measure lens capsule thickness in cadaver eyes.
Acoustic Eaton lens array and its fluid application
Kim, Sang-Hoon; Das, Mukunda P
2016-01-01
A principle of an acoustic Eaton Lens array and its application as a removable tsunami wall is proposed theoretically. The lenses are made of expandable rubber balloons and create a stop-band by the rotating the incoming tsunami wave and reduce the pressure by canceling each other. The diameter of each lens is larger than the wavelength of the tsunami near the coast, that is, order of a kilometer. The impedance matching on the border of the lenses results in little reflection. Before a tsunami, the balloons are buried underground in shallow water near the coast in folded or rounded form. Upon sounding of the tsunami alarm, water and air are pumped into the balloons, which expand and erect the wall above the sea level within a few hours. After the tsunami, the water and air are released from the balloons, which are then buried underground for reuse. Electricity is used to power the entire process.
Metamaterial lens applicator for microwave hyperthermia of breast cancer.
Wang, Gang; Gong, Yu
2009-01-01
Artificial left-handed metamaterial (LHM) provides a new perspective for microwave hyperthermia. Four flat LHM slab lenses can be used to form a focus-flexible applicator for breast tumour hyperthermia. By adjusting microwave sources behind the four flat LHM lenses, microwaves emitted from the sources can be focused tightly at different points in the breast tissue so that necessary heating depth in breast tissue can be achieved. Numerical simulations with a two-dimensional finite-difference time-domain method indicate that hyperthermia with the proposed four-lens applicator of moderate LHM losses could be effective in achieving desired power deposition in a heterogeneous breast model. Temperature distribution obtained by solving the bio-heat transfer equation demonstrates that temperature above 43 degrees C can be maintained in the tumour volume for specific periods of time. Flat slab LHM lenses offer a feasible alternative to traditional mechanically scanned lens applicator and electronically scanned phased-array applicators.
Algorithm design of liquid lens inspection system
Hsieh, Lu-Lin; Wang, Chun-Chieh
2008-08-01
In mobile lens domain, the glass lens is often to be applied in high-resolution requirement situation; but the glass zoom lens needs to be collocated with movable machinery and voice-coil motor, which usually arises some space limits in minimum design. In high level molding component technology development, the appearance of liquid lens has become the focus of mobile phone and digital camera companies. The liquid lens sets with solid optical lens and driving circuit has replaced the original components. As a result, the volume requirement is decreased to merely 50% of the original design. Besides, with the high focus adjusting speed, low energy requirement, high durability, and low-cost manufacturing process, the liquid lens shows advantages in the competitive market. In the past, authors only need to inspect the scrape defect made by external force for the glass lens. As to the liquid lens, authors need to inspect the state of four different structural layers due to the different design and structure. In this paper, authors apply machine vision and digital image processing technology to administer inspections in the particular layer according to the needs of users. According to our experiment results, the algorithm proposed can automatically delete non-focus background, extract the region of interest, find out and analyze the defects efficiently in the particular layer. In the future, authors will combine the algorithm of the system with automatic-focus technology to implement the inside inspection based on the product inspective demands.
A Magnification Lens for Interactive Volume Visualization
LaMar, E; Hamann, B; Joy, K I
2001-07-19
Volume visualization of large data sets suffers from the same problem that many other visualization modalities suffer from: either one can visualize the entire data set and lose small details or visualize a small region and lose the context. In this paper, they present a magnification lens technique for volume visualization. While the notion of a magnification-lens is not new, and other techniques attempt to simulate the physical properties of a magnifying lens, their contribution is in developing a magnification lens that is fast, can be implemented using a fairly small software overhead, and has a natural, intuitive appearance. The issue with magnification lens is the border, or transition, region. The lens center and exterior have a constant zoom factor, and are simple to render. It is the border region that blends between the external and interior magnification, and has a non-constant magnification. They use the perspective-correct textures capability, available in most current graphics systems, to produce a lens with a tessellated border region that approximates linear compression with respect to the radius of the magnification lens. They discuss how a cubic border can mitigate the discontinuities resulting from the use of a linear function, without significant performance loss. They discuss various issues concerning development of a three-dimensional magnification lens.
Trends of contact lens prescribing in Jordan.
Haddad, Mera F; Bakkar, May; Gammoh, Yazan; Morgan, Philip
2016-10-01
To evaluate contact lens prescribing trends among optometrists in Jordan. Optometrists from 173 practices in Jordan were surveyed about prescribing contact lenses in their practice. Practitioners were required to record information for the last 10 patients that visited their practice. Demographic data such as age and gender was obtained for each patient. In addition, data relating to lens type, lens design, replacement methods and the care regime advised to each patient were recorded. Practitioners were required to provide information relating to their education and years of experience. The influence of education and experience with respect to lens prescribing trends was explored using linear regression models for the proportions of lens types fitted for patients. A total of 1730 contact lens fits were analyzed. The mean (±SD) age of lens wearers was 26.6 (±7.9) years, of whom 65% were female. Conventional hydrogel lenses were the most prescribed lenses, accounting for 60.3% of the fits, followed by silicone hydrogel lenses (31.3%), and rigid lenses (8.4%). In terms of lens design, spherical lenses appeared to be most commonly prescribed on monthly basis. Daily disposable lenses were second most prescribed lens modality, accounting for 20.4% of the study sample. Multi-purpose solution (MPS) was the preferred care regimen, with a prevalence of 88.1% reported in the study sample, compared to hydrogen peroxide (1-step and 2-step), which represented only 2.8% of the patients in this study. A relationship was established between the two educational groups for rigid lens prescribing (F=17.4, ptrends among optometrists in Jordan. Contact lens prescribing in terms of lens type, lens design, modality of wear and care regimen agree with global market trends with small variations. This report will help practitioners and the industry to detect any deficiencies in the contact lens market in Jordan, which will ease implementing current and future plans in developing contact
PowerStaTim 1.0 – un nou program statistic de calcul a mărimii efectului și a puterii statistice
Florin A. Sava
2008-01-01
Full Text Available The present paper presents the main characteristics of a new software for computing effect size and statistical power indicators: PowerStaTim 1.0 (Maricuțoiu & Sava, 2007. The first part of the present paper presents the rationale for computing effect size and statistical power in psychological research. The second part of the article introduces the reader to the technical characteristics of PowerStaTim 1.0 and to the processing options of this software.
Fu, Yuwei; Rong, Mingzhe; Yang, Kang; Yang, Aijun; Wang, Xiaohua; Gao, Qingqing; Liu, Dingxin; Murphy, Anthony B.
2016-04-01
SF6 is widely used in electrical equipment as an insulating gas. In the presence of an electric arc, partial discharge (PD) or spark, SF6 dissociation products (such as SF2, SF3 and SF4) react with the unavoidable gas impurities (such as water vapor and oxygen), electrodes and surrounding solid insulation materials, forming several toxic and corrosive byproducts. The main stable decomposition products are SO2F, SO2F2 and SOF2, which have been confirmed experimentally to have a direct relationship with discharge faults, and are thus expected to be useful in the fault diagnosis of power equipment. Various studies have been performed of the main SF6 decomposition species and their concentrations under different types of faults. However, most of the experiments focused on the qualitative analysis of the relationship between the stable products and discharge faults. Although some theoretical research on the formation of main SF6 derivatives have been carried out using chemical kinetics models, the basic data (chemical reactions and their rate constants) adopted in the model are inaccurate and incomplete. The complex chemical reactions of SF6 with the impurities are ignored in most cases. The rate constants of some reactions obtained at ambient temperature or in a narrow temperature range are adopted in the models over a far greater range, for example up to 12 000 K, due to the difficulty in the experimental measurement and theoretical estimation of rate coefficients, particularly at high temperatures. Therefore, improved theoretical models require not only the consideration of additional SF6 decomposition reactions in the presence of impurities but also on improved values of rate constants. This paper is devoted to determining the rate constants of the chemical reactions relating to the main byproducts of SF6 decomposition in SF6 gas-insulated power equipment: SO2F, SOF2 and SO2F2. Quantum chemistry calculations with density functional theory, conventional
Pintwala, Robert; Postnikoff, Cameron; Molladavoodi, Sara; Gorbet, Maud
2015-03-01
Cataracts are the leading cause of blindness worldwide, requiring surgical implantation of an intraocular lens. Despite evidence of leukocyte ingress into the postoperative lens, few studies have investigated the leukocyte response to intraocular lens materials. A novel coculture model was developed to examine macrophage activation by hydrophilic acrylic (poly(2-hydroxyethyl methacrylate)) and hydrophobic acrylic (polymethylmethacrylate) commercial intraocular lens. The human monocytic cell line THP-1 was differentiated into macrophages and cocultured with human lens epithelial cell line (HLE-B3) with or without an intraocular lens for one, two, four, or six days. Using flow cytometry and confocal microscopy, expression of the macrophage activation marker CD54 (intercellular adhesion molecule-1) and production of reactive oxygen species via the fluorogenic probe 2',7'-dichlorodihydrofluorescein diacetate were examined in macrophages. α-Smooth muscle actin, a transdifferentiation marker, was characterized in lens epithelial cells. The poly(2-hydroxyethyl methacrylate) intraocular lens prevented adhesion but induced significant macrophage activation (p intraocular lens), while the polymethylmethacrylate intraocular lens enabled adhesion and multinucleated fusion, but induced no significant activation. Coculture with either intraocular lens increased reactive oxygen species production in macrophages after one day (p intraocular lens, with hydrophilic surfaces inducing higher activation than hydrophobic surfaces. These findings provide a new method of inquiry into uveal biocompatibility, specifically through the quantification of cell-surface markers of leukocyte activation.
Brule, Stephane; Guenneau, Sebastien
2016-01-01
A prerequisite for achieving seismic invisibility is to demonstrate the ability of civil engineers to control seismic waves with artificially structured soils. We carry out large-scale field tests with a structured soil made of a grid consisting of cylindrical and vertical holes in the ground and a low frequency artificial source (< 10 Hz). This allows the identification of a distribution of energy inside the grid, which can be interpreted as the consequence of an effective negative refraction index. Such a flat lens reminiscent of what Veselago and Pendry envisioned for light opens avenues in seismic metamaterials to counteract the most devastating components of seismic signals.
康欣乐; 李明新
2013-01-01
Objective To evaluate the accuracy of axial length and intraocular lens (IOL) measurement in silicone oil - filled eyes using A - scan ultrasound. Methods The cuvette was put with the silicone oil taken from the patients ' eyes, pure silicone oil and balanced salt solution. The speed of ultrasonic wave in these solvent was measured with empir -ical method using Compat tach Ⅱ A/B acoustic instrument of French QUANTEL MEDICAL company . Then the measured axial length was corrected to evaluate the accurate power of IOL . 25 patients who had vitrectomy and silicone oil filled surgery were collected. Firstly, using the recognized acoustic speed of 0x5700 to measure the axial length of the sick eye. Secondly, using the speed by our experiment to measure the sick eye in sitting position and in supine position . Fi-naly, the power of IOL was then calculated through SRK II formula by the axial length in sitting position. They received silicone oil extraction and cataract phacoemulsification and IOL implantation in one operation . 3 months after surgery, all eyes were reexamined and the actual axial length were measured again . The eye axial length and the best correct visual a -cuity were compared before and after the operation. The postoperative refraction and preoperative expected refraction was compared. Results The mean width of colorimetric cuvettes filled with pure Ox5700 silicone oil was (31.440 ±0.011) mm, that filled with the oil taken from patients' eyes was (31.420 ± 0.047 ) mm. There was no difference between them. The width of colorimetric cuvettes filled with the balanced salt solution was 21.07 mm. The recognized acoustic speed of Ox5700 silicone oil was 990 m/s. Before the surgrey, the mean axial length under the acoustic speed of 990 m/s in sili-cone oil tamponade eyes was (23. 219 ±0.125) mm. The mean axial length under the acoustic speed of 1 027m/s in sili-cone oil tamponade eyes was (24. 103 ±0. 135) mm in sitting position and was (24. 116 ±0. 128
Contact lens intolerance: refitting with dual axis lens for corneal refractive therapy
López-López, María; Pelegrín-Sánchez, José Miguel; Sobrado-Calvo, Paloma; García-Ayuso, Diego
2011-01-01
Corneal refractive therapy is a non-surgical procedure whose main purpose is to improve uncorrected visual acuity during the day, without spectacles or contact lenses. We report an adult woman who shows contact lens intolerance and does not want to wear eyeglasses. We used dual axis contact lens to improve lens centration. We demonstrate a maintained unaided visual acuity during one year of treatment. In conclusion, we can consider refitting with dual axis lens for corneal refractive therapy as a non-surgical option for patients who show contact lens intolerance.
Niels Lynnerup
Full Text Available BACKGROUND: Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14C content from the atmospheric carbon dioxide. The (14C content of the lens proteins thus reflects the atmospheric content of (14C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the (14C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric (14C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating. METHODOLOGY/PRINCIPAL FINDINGS: Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation. CONCLUSIONS/SIGNIFICANCE: Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the (14C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA. Potential targets may be nervous tissues in terms of senile or pre
Progressive addition lens design by optimizing NURBS surface
Liu, Yen-Liang; Hsu, Wei-Yao; Cheng, Yuan-Chieh; Su, Guo-Dung
2011-10-01
Progressive addition lenses (PAL) are used to compensate presbyopia, which is induced by losing accommodation of elder eyes. These eyes need different optical power provided by eye glasses while watching objects at different distance. A smaller optical power is required in further distance and a larger one in nearer zone. A progressive addition lens can provides different power requirements in one piece of lens. This paper introduces a whole process of PAL production, from design, fabrication, to measurement. The PAL is designed by optimizing NURBS surface. Parameters of merit function are adjusted to design lenses with different specifications. The simulation results confirm that the power distributes as expected and cylinders are controlled under an acceptable level. Besides, sample lenses have been fabricated and measured. We apply precise-machining to produce the molds for plastic injection. Then, the samples are produced by injecting polycorbonate to the molds. Finally, Ultra Accuracy 3D Profilemeter is used to measure the sample PALs. Practical examinations shows that our designs are achievable and feasible in practice use.
Fabricating customized hydrogel contact lens
Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.
2016-10-01
Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies.
刘杨华; 吴政球; 林舜江
2009-01-01
提出了适用于孤岛运行的微电网三相不平衡潮流计算方法:结合实际,对传统潮流计算方法予以改进,计算中考虑了配电系统各分布式电源的有功、无功控制能力,即电压、频率静态调节特性,考虑了变压器移相角对潮流的影响以及线路参数的相间耦合;算法采用相分量分析,能够应对线路参数三相不平衡、负荷三相不平衡等情况;用牛顿-拉夫逊法求解,易于处理环网结构配电网的潮流计算;不仅能进行三相不平衡潮流分析,还能同时计算出系统的频率.%This paper presented a new method for unbalanced three-phase power flow calculation in islanding micro grid. No balance node was set, while the auto power adjusting of each DGR, the static P-f and V-Q characteristics of each distributed generation resources (DGRs) were considered. The phase shifting in the power flow between the primary and the secondary windings of the transformer caused by the transformer winding connection and the coupling of the lines were also discussed. Using phase component, the three-phase power flow calculation method proposed in this paper can deal with several circumstances, such as asymmetrical line coefficients, and the unbalanced load of three phases. With Newton-Raphson method, it can solve the power flow calculation of the network in ringing topological structure. This work can make both the power flow and the frequency of the power system. This research provides a new reference for real unbalanced three-phase power flow calculation in islanding distributed power generation system.
Plasma Lens for Muon and Neutrino Beams
Kahn,S.A.; Korenev, S.; Bishai, M.; Diwan, M.; Gallardo, J.C.; Hershcovitch, A.; Johnson, B.M.
2008-06-23
The plasma lens is examined as an alternate to focusing horns and solenoids for use in a neutrino or muon beam facility. The plasma lens concept is based on a combined high-energy lens/target configuration. The current is fed at electrodes located upstream and downstream from the target where pion capturing is needed. The current flows primarily in the plasma, which has a lower resistivity than the target. A second plasma lens section, with an additional current feed, follows the target to provide shaping of the plasma for optimum focusing. The plasma lens is immersed in an additional solenoid magnetic field to facilitate the plasma stability. The geometry of the plasma is shaped to provide optimal pion capture. Simulations of this plasma lens system have shown a 25% higher neutrino production than the horn system. Plasma lenses have the additional advantage of negligible pion absorption and scattering by the lens material and reduced neutrino contamination during anti-neutrino running. Results of particle simulations using plasma lens will be presented.
Metasurface lens: Shrinking the camera size
Sun, Cheng
2017-01-01
A miniaturized camera has been developed by integrating a planar metasurface lens doublet with a CMOS image sensor. The metasurface lens doublet corrects the monochromatic aberration and thus delivers nearly diffraction-limited image quality over a wide field of view.
Managing as designing with a positive lens
Avital, M.; Boland, R.J.; Avital, M.; Boland, R.J.; Cooperrider, D.L.
2007-01-01
The role and potential contribution of a positive lens to the design of systems and organizations is the focus of this essay. The positive lens refers to an emerging perspective in the social sciences that emphasizes a positive stance toward our capacity to construct better organizations and technol
Optimization of Zoom Lens with Discrete State of Liquid Lens Elements by Using Genetic Algorithm
Cheng-Mu Tsai
2015-01-01
Full Text Available This paper is to employ liquid lens elements to design a lens with zoom function by using the genetic algorithm (GA optimization. The liquid lens elements used in the proposal can apply voltage adjustment to generate the electrical field that induces the liquid with electric conductivity to vary the surface curvature between two different kinds of liquids. According to the voltage level, the liquid lens element makes the discrete variation of the curvature and thickness realize the zoom function without moving the lens groups so that the overall length can be reduced. However, it is difficult to design the zoom lens under the discrete variation of the curvature and thickness in the liquid lens elements and the mechanical space that is constantly limited. The GA offers a flexible way for lens optimization. We regarded the spot size as the fitness function to look for the optimum curvatures, thickness, and the corresponding statuses of liquid lens elements for the zoom lens. As a result, the zoom lens with constant space can be realized by running the selection, crossover, and mutation operation in the GA optimization.
Feyrer, R.
1994-12-31
A preliminary simulator establishes the maximum possible load change in a pumped storage power plant. The complex hydraulic system of such power plants renders controlling of their operation difficult. The preliminary simulator continuously determines the maximum permissible turbine output and number of pumps at each instance, thereby facilitating power plant operation control. This simulator is installed at the Witznau power plant and is currently undergoing intense testing. It will be integrated into the new process control system installed in 1994. (orig.) [Deutsch] Der Vorabsimulator ermittelt die maximal moegliche Lastaenderung in einem Pumpspeicherwerk. Das komplizierte Wasserfuehrungsystem des Pumpspeicherwerks erschwert die Betriebsfuehrung. Der Vorabsimulator bestimmt kontinuierlich die momentan maximal zulaessige Turbinenleistung und Pumpenanzahl, und erleichtert damit die Betriebsfuehrung des Kraftwerks. Der Vorabsimulator ist im Kraftwerk Witznau installiert und wird derzeit intensiv getestet. Eine Einbindung in die neue Leittechnik, die 1994 installiert wird, ist vorgesehen. (orig.)
Bacterial assay of contact lens wearers.
Hart, D E; Hosmer, M; Georgescu, M; Farris, R L
1996-03-01
The goal of the project was to determine the quantity of bacteria on the contact lens and adjacent areas of the eye. This paper is a quantitative study of the contact lens and ocular aerobic microbiota in a mixed group of daily and extended wear disposable contact lens users. The contact lens, the lower fornix, tears collecting at the lower fornix, and edge of the lower lid at the Meibomian gland margin were assayed for the quantity of bacterial colony forming units (CFU). Eighteen patients wearing 49 disposable high water content hydrogel contact lenses were assayed and the mean lens age was 8.8 +/- 4.6 days. Three patients wore their lenses on a daily wear basis and 15 on an extended wear schedule. Tear samples were obtained with sterile microbial loops and the lens was macerated into small particles with a tissue grinder. The samples were poured onto the surface of chocolate agar plates and incubated at 35 degrees C for 48 h in 5% Co2. The lid margin revealed the greatest bacterial presence (mean = 9.7 CFU; median = 2 CFU; mode = 0 CFU). The lens showed the next greatest presence of CFU (mean = 4.5 CFU; median = 1 CFU; mode = 0). The fornix and tears revealed the least bacterial presence (fornix: mean = 2.6 CFU; median = 0 CFU; mode = 0 CFU). The bacteria were coagulase-negative staphylococci. The bacterial assay of disposable lens wearing contact lens subjects indicates that the lid margins are the greatest source of bacteria with the tears being the lowest. These studies support the concept that in the eye, the lens typically does not possess a large number of bacteria under normal conditions.