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This paper aims to investigate the friction and wear properties of Cr-Ni-Mo-V steel against 440C stainless steel under both water and water–silica mixture lubricant.

The Cr-Ni-Mo-V steel specimens were taken from a forged steel brake disc with the process of quenching at 900°C and tempering at 600°C. The tribological testing was performed using a contact configuration of ball-on-flat with a liquid cell according to the ASTM standard. Detailed examinations on the worn surface were analyzed using a scanning electron microscope.

The results indicate that the friction coefficient and friction damage of the steel sliding under water–silica mixture are higher than those under water. The friction coefficient decreases with increasing load and increases with the sliding speed for the two lubricants. The mass wear rate presents a rising trend with both sliding load and speed. The wear mechanisms of the Cr-Ni-Mo-V steel sliding under the two lubricants are oxidation wear, abrasive wear and fatigue wear.

Because of the chosen tribological testing approach, the research results could not describe the tribological performance of the brake disc accurately during actual braking process of the high-speed train. Therefore, researchers are encouraged to test the proposed propositions further.

This study shows that the tribology behavior of the Cr-Ni-Mo-V steel with water or water–silica mixture lubrications helps the industrial firms and academicians to work on the wear of the brake disc in rainwater or wet environment.

The purpose of this paper is to examine the existence of operational stickiness, and explores the relationship between operational stickiness and the likelihood of survival. Furthermore, the authors investigate this relationship in different manufacturing industries.

Using a large sample of more than 200,000 new manufacturing small and medium enterprises between 2000 and 2013 in China, the authors use the survival analysis method to investigate the non-linear relationship between operational stickiness and the likelihood of survival.

The authors demonstrate the existence of operational stickiness, such as inventory stickiness, property, plant, and equipment (PPE) stickiness, and labor stickiness. Next, the authors find the inverted U-shaped relationship between operational stickiness and the likelihood of survival. Furthermore, the authors document the differential effect of operational stickiness on the likelihood of survival in different industries.

Managers can improve the firm’s likelihood of survival by maintaining a moderate inventory stickiness and PPE stickiness. However, managers should not adopt sticky labor management in manufacturing industries.

This paper may be the first study to demonstrate the existence of operational stickiness, and confirm the inverted U-shaped relationship between operational stickiness and the likelihood of survival.

The purpose of this paper is to examine the impact of operational stickiness on product quality. Particularly, it analyzes the moderating effect of product diversification on the relationship between operational stickiness and product quality of exporting firms from China.

Using a sample of 3,567 exporting firms between 2002 and 2012 in China, this paper develops a fixed effect model to demonstrate the nonlinear relationship between operational stickiness and product quality.

Results show that operational stickiness has an inverted U-shaped impact on product quality, while inventory stickiness, property, plant and equipment (PPE) stickiness and labor stickiness are used to measure operational stickiness. Furthermore, the impact of operational stickiness on product quality is found to be moderated by product diversification.

Managers can achieve an optimal level of product quality by adjusting the level of operational stickiness. Firms with excessive operational stickiness should appropriately reduce the degree of stickiness to improve product quality. Besides, managers who focus on product quality should be cautious in adopting the product diversification strategy and be wary of the loss of product quality this strategy may cause.

This paper is the first study that has empirically validated the inverted U-shaped relationship between operational stickiness and product quality, and confirmed the moderating effect of product diversification on the relationship between operational stickiness and product quality. It provides a new idea to improve product quality by operational management.

The purpose of this paper is to investigate the impacts of different gray markets’ structures on both supply chain decisions and associated profits.

Within the context of gray markets, using game theory approach in this paper, supply chains have been considered as assets of manufacturers, distributors and speculators, within which manufacturers sell products to distinctive markets either directly or through authorized distributors, while speculators buy products from a lower price market and then sell them in a higher price market. Our study has examined different decision variables within such a framework.

Considering a situation where one manufacturer sells its products either directly in one market (Market 1) or through its authorized distributor (Market 2), due to different products prices in both markets, results have shown that, when market elasticity is less than its critical value, a speculator can sell a gray market product arbitrage in market 2, whereas when the market elasticity is greater than its critical value, a speculator can sell a gray market product arbitrage in market 1. In addition, manufacturers—as leaders of Stackelberg game—are always the most profitable stakeholders within a gray market supply chain.

In this study, equilibrium results for each market have been obtained, optimal results have been compared, and accordingly, valuable insights have been developed. Such results would help managers to take better managerial decisions, as well as strategizing policies in gray markets.

In this paper, we have considered a gray market where both distributors and speculators exist and act as parallel channels. To the best of our knowledge, the extant literature focuses either on distributors or speculators, but never concurrently on both. In fact, the coexistence of one distributor and one speculator in a gray market will impact their own decisions, as well as both decisions and profits of other stakeholders, and hence, will exert an impact on the manufacturer side.

This review aims to give an overview about zinc oxide (ZnO) based gas sensors and the role of doping in enhancing the gas sensing properties. Gas sensors based on ZnO thin film are preferred for sensing applications because of their modifiable surface morphology, very large surface-to-volume ratio and superior stability due to better crystallinity. The gas detection mechanism involves surface reaction, in which the adsorption of gas molecules on the ZnO thin film affects its conductivity and reduces its electrical properties. One way to enhance the gas sensing properties is by doping ZnO with other elements. A few of the common and previously used dopants include tin (Sn), nickel (Ni) and gallium (Ga).

In this brief review, previous works on doped-ZnO formaldehyde sensing devices are presented and discussed.

Most devices provided good sensing performance with low detection limits. The reported operating temperatures were within the range of 200̊C –400̊C. The performance of the gas sensors can be improved by modifying their nanostructures and/or adding dopants.

As of yet, a specific review on formaldehyde gas sensors based on ZnO metal semiconductors has not been done.