Optical biometry intraocular lens power calculation using different formulas in patients with different axial lengths

AIM: To investigate the predictability of intraocular lens (IOL) power calculation using the IOLMaster and different IOL power calculation formulas in eyes with various axial length (AL). METHODS: Patients were included who underwent uneventful phacoemulsification with IOL implantation in the Department of Ophthalmology, Far Eastern Memorial Hospital, Taipei, Taiwan, China from February 2007 to January 2009. Preoperative AL and keratometric values (Ks) were measured by IOLMaster optical biometry. Patients were divided into 3 groups based on AL less than 22mm (Group 1), 22-26mm (Group 2), and more than 26mm (Group 3). The power of the implanted IOL was used to calculate the predicted postoperative spherical equivalence (SE) by various formulas: the Haigis, Hoffer Q, Holladay 1, and SRK/T. The predictive accuracy of each formula was analyzed by comparing the difference between the actual and predicted postoperative SE (MedAE, median absolute error). All the patients had follow-up periods exceeding 3 months. RESULTS: Totally, there were 200 eyes (33 eyes in Group 1, 92 eyes in Group 2, 75 eyes in Group 3). In all patients, the Haigis had the significantly lower MedAE generated by the other formulas (P【0.05). In Group 1 to 3, the MedAE calculated by the Haigis was either significantly lower or comparable to those calculated by the other formulas.CONCLUSION: Compared with other formulas using IOLMaster biometric data, the Haigis formula yields superior refractive results in eyes with various AL.

Research and Experimental Application of Empirical Formulas to Calculate Riverbank Erosion in Tien River in the Mekong Delta

In recent years,the problem of riverbank and coastal erosion in the MD(Mekong Delta)is very complicated;landslides occur in most of the inland and coastal provinces.Most riverbank landslides occur gradually,but in contrast to sudden landslides that cause great damage,occur with increasing frequency.This shows that the trend of riverbank erosion will be more complicated and more frequent,especially in the context of extreme weather changes and changes in hydrological regime in the next time.Statistics from the authorities show that,if in 2010 the whole region had nearly 100 landslide points;by 2020 it had increased to more than 680 points;in which Dong Thap in the Tien River is one of the two localities with the most serious riverbank erosion.Currently,there are many methods used to assess and forecast the level of riverbank erosion in specific areas,such as:method of document analysis,measurement data;physical model;mathematical models and empirical formulas.In this study,the empirical formula is used to calculate the landslide level for the Tien River section in Cao Lanh,Dong Thap province.The calculation results according to the empirical formula have a certain agreement with the actual data,the correlation coefficient is 0.90 and the Nash coefficient is 0.78,the relative error of less than 15%is 80%of the cross-section.Such results have shown the possibility of applying empirical formulas to establish and calculate for other landslide areas along the banks of Hau River and MD.

Shear resistance performance of steel-concrete-steel composite shear wall

For a deeper understanding of the shear resistance performance of the steel-concrete-steel composite shear wall, the main influence factors such as the thicknesses of the steel plates and the concrete, the strength grades of the concrete and the span-depth ratios of the composite wall, which have impacts on the shear resistance performance of the composite shear wail, are analyzed by the numerical simulation method. Meanwhile, the simplified calculation formulae of the initial elastic lateral-resisting stiffness and the shear bearing capacity of the composite shear wall are also proposed. The research shows that with the increase in the thicknesses of the steel plates and the concrete and the increase in the strength grades of the concrete, the shear performance of the shear wall improves obviously; the span-depth ratios of the composite wall have a significant effect on the initial elastic lateral- resisting stiffness, but a small effect on the shear bearing capacity. Comparing the results of the simplified calculation formulae with those of the nonlinear finite element method, it is obvious that the presented formulae are reasonable and meet the real force state of the structure. These conclusions can serve as a preliminary design reference for the steel-concrete- steel composite shear wall.

Behavior of galvanized steel tube subjected to web crippling

The details of a research study of galvanized steel tube under web crippling were presented. A total of 48 galvanized steel square hollow sections with different boundary conditions, loading conditions, bearing lengths and web slenderness were tested. The experimental scheme, failure modes, load-displacement curves and strain intensity distribution curves were also presented. The investigation was focused on the effects of loading condition, bearing length and slenderness on web crippling ultimate capacity, initial compressive stiffness and ductility of galvanized steel tube. The results show that web crippling ultimate capacity increases linearly with the increase of the bearing length under EOF and IOF loading condition. In the end-flange and ITF loading conditions, strain intensity of the centerline of web reaches the peak and decreases progressively from central web to flanges. Finite element models were developed to numerically simulate the tests in terms of failure modes and ultimate capacity. Web crippling strength of galvanized steel tube increases linearly with the increase of the ratio of the bearing length to web thickness and decrease of web slenderness. The effect of ratio of galvanized layer thickness to web thickness on web crippling strength is small. Based on the results of the parametric study, a number of calculation formulas proposed in this work can be successfully employed as a design rule for predicting web crippling ultimate capacity of galvanized steel tube under four loading and boundary conditions.

Experimental Study of Structure Shock Vibration in Soil Caused by Explosion of Conventional Weapons

When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments. The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure.

Mathematical Modeling of Landfill Gas (MSW)—Production of Gas with Methane Gas Content from Landfills (MSW)

The municipal solid waste (msw) is a source of landfill gas (msw)—with methane gas content. Preoccupations for landfill gas (msw) management date back since 1976 when, at a landfill (msw) in California (USA), it turned out practically that the landfill gas (msw) with methane gas content contains a gas with high caloric value that can be collected and used for economic purposes. The landfill gas (msw) contains methane gas (30% - 60% volume), carbon dioxide (45% - 50% volume), hydrogen sulfide and other gases. Methane gas, carbon dioxide, nitrous oxide and other gases are listed in Kyoto Protocol as high greenhouse gases. Their ecological-rational management is both a national and global preoccupation. In terms of greenhouse gases, especially methane gas, the landfill (msw) is held responsible for 3.5% - 5% of the total global greenhouse gases. Practically, the quantitative estimation of the methane gas in a municipal solid waste landfill can be done by measuring the landfill gas (msw) flow in an extraction-collection well. In Romania, a quantitative estimation relationship of methane gas from deposits (msw) was made, approaching the problem in a different way. This paper presents the calculation formula, the working algorithm, the municipal waste landfill equation and the NOMOGRAMA of a municipal solid waste landfill (msw). The NOMOGRAMA allows us to define the values for parameter -m- (number of months needed for an amount of municipal solid waste (msw) to degrade, starting with the year from which the landfill gas (msw) emission with methane gas content is calculated). Taking into account the environmental conditions for each location of municipal solid waste landfill, the calculation uses various indexes and approximations, while the fundamental parameter remains -m- defined by the NOMOGRAMA of the municipal solid waste landfill (msw). A municipal solid waste landfill (msw) is a conglomerate of waste with various biodegradation periods between 2 - 3 years and 5 - 10 - 30 years. Degradation of waste (msw) in to dissolved organic carbon will take place in a number of months defined -m- starting with the year from which the methane gas emission with the NOMOGRAMA of the municipal solid waste landfill (msw) is calculated. The -m- values for the year of the quantitative emission of methane gas can be also done analytically, which requires good experience in the ecologic-rational management of the municipal solid waste (msw).

Determation method for water content of diesel contaminated soil

With the increasing researches on geotechnical properties of the diesel contaminated soil( DCS),the water content measured is indispensable part during the early period. In this study,the relative error of water content measurement using the traditional method is as high as 20. 78%,which is no longer suitable for contaminated soil. Through a series of tests to measure the loss coefficient of diesel in the drying time,the authors finally proposed a modified calculation formula for test samples. The results show that the maximum relative error calculated by using the modified formula is 0. 96%,far lower than that of traditional formula,which can provide accurate data for further study of diesel contaminated soil.

Formulas of exact calculation of discrepancy of low-dimensionalfinite point sets (Ⅱ)

This letter is a continuation of refs.[1] and [2]. Let d≥2, Sd={uk（1≤k≤n）} be a finiteset of points in the d-dimensional unit cube [0, 1)d, where uk=(u1,k, u2,k,…,ud,k)

Calculation Method of Wave Forces on Large Round-Ended Caisson Foundation

This paper presents an analytical formula for estimating the longitudinal wave forces on a large roundended caisson foundation. The establishment of the formula is based on the superposition of the theoretical formula of wave forces on a large circular cylinder and the empirical formula of wave forces on a large rectangular cylinder. With the formula transformed into an inertial force form, a specific inertia coefficient with an exact expression is extracted from the formula. The numerical calculations of the wave forces on round-ended cylinders are carried out by the boundary-element method. The undetermined coefficients in the expression of the inertial coefficient are determined by the numerical results. It is obvious that the numerical values can be well expressed by the computation values from the established formula. By a model experiment carried out in laboratory wave flume, the correctness of the analytical formula is further verified by the measured wave forces on a test model of a round-ended bridge caisson foundation. The comparison shows that the experimental forces can be approximately estimated by this simple calculation method.

ON CALCULATIONS OF THE DRAG COEFFICIENT Cd AND THE FALL VELOCITY ω OF SPHERICAL BODIES

A host of authors have proposed some theoretical and experimental formulas in hydromechanics concerning the calculation of the drag coefficient Cd of spherical bodies. But all of the existing Cd formulas hold true only at small Reynolds numbers and are restricted within certain flowing range.As regards the fall velocity ω of spherical bodies, there is yet no formula applicable to each flowing range and to a direct expression and calculation of the fall velocity ω.In view of these, from N-S equations, and meanwhile based on measured data and complicated calculations, the author has developed and proposed the following results:(1) The drag coefficient (2) The dimensionless fall velocity where Es, Ω* and constants etc. are indicated in detail in this paper.Through laborious calculation in lgRe<5 larger range, the verification proves that our results well agree with the measured data. And the leading features of formulas of this paper are: (1) simple in form, (2) convenient for general use, (3) preferable on the part of the precision and applicability.Finally, to introduce this process and to illustrate the temperature effects on the fall velocity ω, some examples are discussed in this paper.