Estimating strength properties of geopolymer self-compacting concrete using machine learning techniques

tThere has been a persistent drive for sustainable development in the concrete industry.While there are series of encouraging experimental research outputs, yet the research fieldrequires a standard framework for the material development. In this study, the strengthcharacteristics of geopolymer self-compacting concrete made by addition of mineral admix-tures, have been modelled with both genetic programming (GEP) and the artificial neuralnetworks (ANN) techniques. The study adopts a 12M sodium hydroxide and sodium sili-cate alkaline solution of ratio to fly ash at 0.33 for geopolymer reaction. In addition to theconventional material (river sand), fly ash was partially replaced with silica fume and gran-ulated blast furnace slag. Various properties of the concrete, filler ability and passing abilityof fresh mixtures, and compressive, split-tensile and flexural strength of hardened concretewere determined. The model development involved using raw materials and fresh mix prop-erties as predictors, and strength properties as response. Results shows that the use of theadmixtures enhanced both the fresh and hardened properties of the concrete. Both GEP andANN methods exhibited good prediction of the experimental data, with minimal errors.However, GEP models can be preferred as simple equations are developed from the process,while ANN is only a predictor

Thermal insulation and mechanical characteristics of cement mortar reinforced with mineral wool and rice straw fibers

Building insulation is an essential requirement for buildings located in areas of varying temperature conditions. However, the conventional building insulation techniques accrue high cost and consume resources. This work aimed to evaluate the use of mineral wool and rice straw to improve Portland cement mortar’s thermal insulating properties. Samples of 40x40x160 mm mortar were produced with cement and sand, but varying mineral wool and rice straw constituents from 0 to 50% in weight. Water absorption, flexural and compressive strengths, thermal conductivity were performed in samples with and without mineral wool and rice straw addition.The microstructure of mortars was analyzed using scanning electron microscopy (SEM). It was observed that reinforcing mortars with mineral wool and rice straw fibers yielded a significant drop in the mortar’s thermal conductivity, improving their insulative abilities. Although the addition of fibers, in turn, deferred the mechanical performance in some mixes, however, it was not too significant or below workable standards. The performed tests prove the feasibility of adopting the selected fibers for insulating Portland cement mortars

Comparison of pre-incision and single-stepped clear corneal incision in phacoemulsification surgery

intraocular lens (IOL) implantation throughout the world. The availability of foldable IOLs that can be inserted though small unsutured phacoemulsification incisions has created a trend away from scleral tunnel incisions to clear corneal incisions Clinical outcomes of cataract surgery are influenced by many factors, including the blade used to create the incision, the phacoemulsification apparatus, and the IOL used and mode of insertion, which together constitute a surgical system, the outcomes of which are restricted by the best performance of each component. Identifying surgical methods to provide the best postoperative visual acuity and the fastest restoration of visual function by reducing surgically induced astigmatism remain a challenge for cataract surgeons 3 . Several studies have investigated the induced astigmatism after various types of small incisions and various locations including superior, superonasal, superotemporal, and temporal The aim of this prospective study was to compare the postoperative keratometric corneal refractive changes after phacoemulsification surgery between pre-incision and single stepped clear corneal incision techniques. CONCLUSIONS: Using pre-incision and single stepped clear corneal incision techniques in phacoemulsification surgery showed no difference on corneal refractive power changes. Preincision technique can be used for smoother corneal incision in cataract surgery especially for the beginners

Petroleum-Refining Industry Business Interruption Losses due to Hurricane Katrina

Hurricane Katrina had a significant destructive effect on the Gulf Coast's petroleum-refining industry. In many cases, refineries sustained considerable damage and had to suspend operations for extended periods of time. Multiple Gulf Coast refineries filed substantial business interruption loss insurance claims following Hurricane Katrina's disruption of their production. This paper presents a methodology to calculate refinery business interruption losses taking into account the effect of Hurricane Katrina on input and output market prices during the period of restoration. Our results indicate that adjusting for Hurricane Katrina's effects on crude oil and petroleum product market prices significantly changes the magnitude of refinery business interruption loss claims.

Does severity of dermatochalasis in aging affect corneal biomechanical properties?

Kurşat Atalay, Ceren Gurez, Ahmet Kirgiz, Kubra Serefoglu Cabuk Department of Ophthalmology, Bagcilar Training and Research Hospital, Istanbul, Turkey Purpose: The aim of this study was to investigate the possibility of a relationship between corneal biomechanical properties and different grades of dermatochalasis.Patients and methods: Patients were assigned to four groups according to the severity of their dermatochalasis: normal (Group 1), mild (Group 2), moderate (Group 3), and severe (Group 4). An Ocular Response Analyzer device was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), and corneal-compensated intraocular pressure (IOPcc).Results: We found no significant differences in the mean values of the CH, CRF, and IOPcc of all groups (P=0.75, P=0.93, and P=0.11, respectively). However, CH and IOPcc were negatively correlated in Group 1, Group 2, and Group 3 patients (P=0.013, r=−0.49; P=0.015, r=−0.52; and P=0.011, r=−0.47, respectively), but this correlation was not apparent in the Group 4 patients (P=0.57, r=0.12). CRF and IOPcc were correlated, but only in Group 4 (P=0.001, r=0.66).Conclusion: Severe dermatochalasis was associated with altered corneal biomechanical properties. Some of the important visual consequences of dermatochalasis and related diseases (such as floppy eyelid syndrome) can be understood by considering corneal biomechanical alterations. Keywords: cornea, dermatochalasis, corneal hysteresis, corneal resistance factor, corneal biomechanical propertie

Scheimpflug camera combined with placido-disk corneal topography and optical biometry for intraocular lens power calculation

The purpose of this study was to compare the keratometry (K) values obtained by the Scheimpflug camera combined with placido-disk corneal topography (Sirius) and optical biometry (Lenstar) for intraocular lens (IOL) power calculation before the cataract surgery, and to evaluate the accuracy of postoperative refraction. 50 eyes of 40 patients were scheduled to have phacoemulsification with the implantation of a posterior chamber intraocular lens. The IOL power was calculated using the SRK/T formula with Lenstar K and K readings from Sirius. Simulated K (SimK), K at 3-, 5-, and 7-mm zones from Sirius were compared with Lenstar K readings. The accuracy of these parameters was determined by calculating the mean absolute error (MAE). The mean Lenstar K value was 44.05 diopters (D) ±1.93 (SD) and SimK, K at 3-, 5-, and 7-mm zones were 43.85 ± 1.91, 43.88 ± 1.9, 43.84 ± 1.9, 43.66 ± 1.85 D, respectively. There was no statistically significant difference between the K readings (P = 0.901). When Lenstar was used for the corneal power measurements, MAE was 0.42 ± 0.33 D, but when simK of Sirius was used, it was 0.37 ± 0.32 D (the lowest MAE (0.36 ± 0.32 D) was achieved as a result of 5 mm K measurement), but it was not statistically significant (P = 0.892). Of all the K readings of Sirius and Lenstar, Sirius 5-mm zone K readings were the best in predicting a more precise IOL power. The corneal power measurements with the Scheimpflug camera combined with placido-disk corneal topography can be safely used for IOL power calculation. © 2016, Springer Science+Business Media Dordrecht

The Effect of Pseudoexfoliation and Pseudoexfoliation Induced Dry Eye on Central Corneal Thickness

Purpose/aim of the study: The aim of this study is to investigate the effect of pseudoexfoliation (PEX) and PEX-induced dry eye on central corneal thickness (CCT).Materials and methods: This cross-sectional study consists of total 270 eyes of 135 patients (67 females, 68 males) in total. After excluding the PEX (-) 32 eyes with PEX in the other eye, totally 130 eyes in PEX (-) group and 108 eyes in the PEX (+) group were included in the study. The PEX (+) group was regrouped as PEX syndrome (80 eyes of 50 patients) and PEX glaucoma (28 eyes of 20 patients).Results: In the PEX (-) group, the mean Schirmer test result was 12 ± 4 mm (4-25 mm), in the PEX syndrome group 10 ± 4 mm (4-22 mm), in the PEX glaucoma group 9 ± 3 mm (4-15 mm). The difference among the PEX (-) group, the PEX syndrome and the PEX glaucoma groups was statistically significant (p < 0.001, p < 0.001, respectively). In the PEX (-) group, the mean tear break up time test result was 11 ± 2 s (5-16 s), in the PEX syndrome group 8 ± 3 (3-16 s), in the PEX glaucoma group 8 ± 3 s (5-15 s). Mean CCT result was 544 m in the PEX (-), 521 m in the PEX syndrome group and 533 m in the PEX glaucoma group. The difference among the PEX (-) group, the PEX syndrome and the PEX glaucoma groups was significant (p < 0.001, p = 0.030, respectively). There was a significant (+) correlation between intraocular pressure and CCT in the eyes with PEX (r = 0.307, p = 0.001). However, there was no statistically significant correlation between CCT, Schirmer and tear break up time tests in the eyes with PEX.Conclusions: PEX material can cause decrease in tear film secretion and disturb tear film stability. There is no effect of PEX-induced dry eye on CCT. Lower CCT values in the eyes with PEX material may be a result of decrease in corneal stromal cell density. Moreover, higher CCT values may be because of decreased endothelial cells in PEX glaucoma patients. © 2015 Taylor and Francis Group, LLC