Lack of driver's knowledge about the abrupt changes in pavement's friction and poor performance of the vehicle's stability, traction, and ABS controllers on the low friction surfaces are the most important factors affecting car crashes. Due to its direct relation to vehicle stability, accurate estimation of tire-road friction is of interest to all vehicle and tire companies. Many studies have been conducted in this field and researchers have used different tools and have proposed different algorithms. This literature survey introduces different approaches, which have been widely used to estimate the friction or other related parameters, and covers the recent literature that contains these methodologies. The emphasize of this review paper is on the algorithms and studies, which are more popular and have been repeated several times. The focus has been divided into two main groups: experiment-based and model-based approaches. Each of these main groups has several sub-categories, which are explained in the next few sections. Several summary tables are provided in which the overall feature of each approach is reviewed that gives the reader the general picture of different algorithms, which are widely used in friction estimation studies.

Pruritus is a common complaint in patients undergoing maintenance hemodialysis. The pathophysiology of pruritus in these patients is not well known, but the role of histamine release from mast cells has been reported. According to the inhibitory effects of zinc on histamine release and reported low levels of serum zinc in hemodialysis patients, we aimed to evaluate the effects of zinc sulfate for the relief of pruritus in these patients. This double-blind, randomized, placebo-controlled trial was conducted on 40 adults with end stage renal disease (ESRD) who were on maintenance hemodialysis in two university hospitals in Isfahan, Iran. Patients were randomized to receive either zinc sulfate (440 mg/day) or placebo for two consecutive months. Pruritus was assessed at baseline and then every two weeks using a numerical rating scale from 0 to 10 until one month after treatment. Drug side effects were also assessed along with pruritus. There were 40 patients with a mean age of 55.5 ± 15.2 (72.5% male) who completed the study. The two groups were similar in baseline characteristics. Pruritus was decreased in both groups after treatment but there was a significantly greater decrease in the zinc sulfate group compared with placebo (P = 0.018). Patient compliance was good and no severe side effects were observed. Zinc sulfate (440 mg/day) is more effective than placebo for the relief of pruritus in patients under maintenance hemodialysis. Further studies with larger sample size, longer treatment duration and follow-up and with various dosages of zinc sulfate are recommended.

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Modeling the real contact area plays a key role in every tribological process, such as friction, adhesion, and wear. Contact between two solids does not necessarily occur everywhere within the apparent contact area. Considering the multiscale nature of roughness, Persson proposed a theory of contact mechanics for a soft and smooth solid in contact with a rigid rough surface. In this theory, he assumed that the vertical displacement on the soft surface could be approximated by the height profile of the substrate surface. Although this assumption gives an accurate pressure distribution at the interface for complete contact, when no gap exists between two surfaces, it results in an overestimation of elastic energy stored in the material for partial contact, which typically occurs in many practical applications. This issue was later addressed by Persson by including a correction factor obtained from the comparison of the theoretical results with molecular dynamics simulation. This paper proposes a different approach to correct the overestimation of vertical displacement in Persson’s contact theory for rough surfaces with self-affine fractal properties. The results are compared with the correction factor proposed by Persson. The main advantage of the proposed method is that it uses physical parameters such as the surface roughness characteristics, material properties, sliding velocity, and normal load to correct the model. This method is also implemented in the theory of rubber friction. The results of the corrected friction model are compared with experiments. The results confirm that the modified model predicts the friction coefficient as a function of sliding velocity more accurately than the original model.