An approach for improving the precision on short-range electronic distance measurement trigonometry
Consider the trigonometric leveling method is simple, flexible and less limited by terrain conditions, it commonly used to inconveniently implemented area. Through the total station rapid development, the horizontal distance measuring between station and target for the traditional triangulation has been substituted by a slope from the Electronic Distance Measurement(EDM) measured. When combined with the appropriate methods of observation and error correction, short-range EDM trigonometric levelingshould be able to improve the accuracy levels of precision leveling. It can be enhanced the efficiency of leveling jobs. The main error of short-range EDM trigonometric leveling is from atmospheric refraction, earth curvature and measurement error of height of instrument and prismatic. The first two errors can be reduced by reciprocal observation and intermediate point. Moreover, intermediate point just only measure the prismatic height between start and end point of the measuring leveling line, The results accuracy and observation efficiency is increased. In this study, about 2km selected sections of Highway 84 at Tainan Yujing District is chosen be an experimental zone. Three kinds of closed leveling line, 200m, 400m and 600m is consisted in this measured planning. Then, non-reciprocal observation, reciprocal observation and intermediate point are introduced to implement the measurement. Experimental results show that the EDM triangle elevation for 600m range or less, the fourth-level observation precision can be achieved in non-reciprocal observation. However, the loop closure error will be caused no any grade leveling accuracy. For the reciprocal observation or intermediate method, third-level precision of measurement accuracy and loop closure error can be accomplished. The results show that the short-range EDM triangle elevation has a higher level of feasibility to instead of the traditional measure.
Precise Height Determination Using Leap-Frog Trigonometric Leveling
Precise leveling has been used for the determination of accurate heights for many years. The application of this technique is difficult, time consuming, and expensive, especially in rough terrain. These difficulties have forced researchers to examine alternative methods of height determination. As a result of modern high-tech instrument developments, research has again been focused on precision trigonometric leveling. In this study, a leap-frog trigonometric leveling (LFTL) is applied with different sight distances on a sample test network at the Selcuk University Campus in Konya, Turkey, in order to determine the optimum sight distances. The results were compared with precise geometric leveling in terms of precision, cost, and feasibility. Leap-frog trigonometric leveling for the sight distance S=150 m resulted in a standard deviation of ±1.87 mm∕km and with a production speed of 5.6 km∕day .
Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems
Abstract Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.