In this paper, the method of determining thermal contact resistance of wavy surfaces is discussed exactly. For determining the thermal contact resistance of real contacts, a new method has been presented. In this method, assuming a regular sinusoidal surface profile, the real contact area in terms of applied forces has been determined. Then thermal contact resistance has been calculated. Testing 6 kinds of insulator’s combinations with wavy surfaces has approved the reliability of the analysis. The results of experiments and analysis had good agreement with each other.

Different types of contact, including contact between node pairs, any-contact of nodes, and contacts of the entire network, are used to characterize social relations in mobile social networks. Different modes of routing, from the point of view of message delivery semantics, encompass unicasting, multicasting, any-casting, and broadcasting. Studies have shown that using probability distribution functions of contact data, which is mainly assumed to be homogeneous for nodes, improves the performance of these networks. However, there exists an important challenge in studies on distributions. A lot of works apply the distribution of one type of contact to other types. Hence in routing applications, it causes to use of the distribution of one type of contact for any mode of routing. This study provides a complete solution to model each type of homogeneous contact data distribution and to use them in different modes of routing. We propose a routing algorithm that uses this new model. Results show that our solution improves the average latency of comparing methods Epidemic, TCCB, and DR about 3.5-times, 30%, and 45%, respectively. It achieves a delivery rate of about 5% and 6%, and average latency about 6% and 8% better than that of DR and TCCB, respectively.

One of the most important issues in agricultural machinery section is tyre-soil interactions. In this study, a single wheel tester was used to follow experiments in controlled conditions in a soil bin. A Goodyear 12. 4-28, 6 ply tractor drive tyre was operated at three vertical loads of 6, 9 and 12 kN, three inflation pressures of 80, 120 and 160 kPa and three moisture content of soil: 11. 20, 14. 86 and 18. 68 % d. b to investigate the effect of the variables on these parameters: contact area, contact pressure, compaction, and soil apparent electrical conductivity. It was found that medium contact pressure had a direct relation with vertical load, inflation pressure and moisture content. A regression model with R-square of 0. 946 was achieved to predict contact pressure. Soil electrical conductivity changes was predicted with acceptable determination coefficient of 0. 850 by using of vertical load, inflation pressure and moisture content. Determination coefficient magnitude for models to predict resistance to soil penetration (cone index) using soil apparent electrical conductivity, decreased when moisture content was increased. The vertical load and inflation pressure were found two factors controlling the soil apparent electrical conductivity changes in low and high moisture content, respectively. Error percentage in using soil apparent electrical conductivity parameter to estimate the penetration resistance increased with increasing moisture content.

Nowadays, due to the need for miniaturization, small scale resistance spot welding is of interest. The key factor that determines the nugget size is contact resistance. In this paper a new equation is provided to calculate the electrical contact resistance. The model can predict the high temperature contours and the nugget configuration efficiently. Also, a set-up was constructed to verify the model and investigate the effects of parameters on the mechanical properties of Hastelloy X welded joints. DOE analysis is done to recognize the effect of parameters on the nugget diameter, maximum load, and nugget height. It was concluded that the size of the nugget enlarges by increasing welding current and time. The nugget diameter decreases with increase of force.

Among various dissipating mechanisms, the viscoelastic effect of rubber material on creation of rolling resistance is responsible for 10-33% dissipation of supplied power at the tire/road interaction surface. So, evaluating this kind of loss is very essential in any analysis concerned with improving the fuel consumption of vehicles and resultantly energy savage. Hysteretic loss is a fraction of stored strain energy of tire which is dissipated during the rotational motion. In all related references and published articles, the hysteretic loss per revolution of tire is commonly considered as the rolling resistance. However, a reasonable approximation of stresses and strains time histories is very crucial for evaluating the amount of hysteretic loss. Based on the results of 3D static contact analysis, an efficient in-house program coded in Matlab is used for estimating the time variation of stress-strain cycles at different points of a rolling tire. Half the difference between maximum and minimum principal values of six stress and strain components can be used for evaluating the hysteretic loss during one revolution of a rolling tire. The results closely match the related experimental and numerical investigations.

The objective of this research is characterizing the effect of Nano-Zinc oxide (nano-ZnO) dispersions on leach resistance and contact angle of beech wood (Fagus orientalis Lipsky). The Beech wood was cut into standard dimension, and oven dried after treating with nano-Zno solution, based on immersion method. Three treating nano-Zno solution levels: (o, 20000 and 40000 ppm), and two thermal treating levels: (60 and 120 o C) were selected. After conditioning, leaching tests were performed and contact angle of samples after 1 and 10 seconds were measured. The results showed that by increasing of the nano material concentration and the temperature, the contact angle increased. In tenth second, the minimum and maximum angles were 53.30o and 90.07 o which observed for untreated sample and for 40000 ppm concentration and 120 o C temperatures, respectively. Improving on contact angle represents the significant reduction in wettability property of surface in treated wood. Results of leaching test implied that effect of increment of nano-zno concentration was negligible, while the temperature increasing resulted in nano-ZnO stabilization.