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Article
Publication date: 1 October 1997

Kunhong Kim and Yong‐Yil Choi

Seeks to present the detailed empirical study of contemporary business fluctuations in Korea. Follows the methodology of modern business cycle research in conducting an…

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Abstract

Seeks to present the detailed empirical study of contemporary business fluctuations in Korea. Follows the methodology of modern business cycle research in conducting an atheoretical statistical analysis of the cyclical properties of key aggregate time series. Shows, by analysis, that many of the cyclical regularities documented for developed countries also exist in Korean business cycles. Regularities include the relative volatilities of many expenditure components and the co‐movement of real and nominal variables with output. Particularly of note is the counter‐cyclicality of prices. Posits that counter‐cyclicality of prices signals the importance of supply side shocks in Korean business fluctuations. Reveals, in the analysis, that the fluctuation in the import price of oil may have been the major source of Korean business cycles. States that analysis has also revealed that there are some idiosyncrasies in Korean business cycles. Net exports are significantly pro‐cyclical and lead the cycle for most of the period under study.

Details

Journal of Economic Studies, vol. 24 no. 5
Type: Research Article
ISSN: 0144-3585

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Article
Publication date: 6 October 2022

Kunhong Hu, Yan Miao and Ziyan Lu

This paper aims to explore the preparation and tribological performance of MoS2 nanoparticles supported on fly ash (FA) microparticles.

119

Abstract

Purpose

This paper aims to explore the preparation and tribological performance of MoS2 nanoparticles supported on fly ash (FA) microparticles.

Design/methodology/approach

FA was activated by NaOH, oleic acid and HCl to obtain three modified FA samples. Nano-MoS2 was deposited on them to form MoS2/FA additives for poly-α-olefin (PAO) modification. Tribological tests were conducted on a reciprocating rig through the ball-on-disk friction manner. Using X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, Raman spectrometer and element analyzers, the products and their lubrication mechanisms were characterized.

Findings

At 1.5 Wt.%, nano-MoS2 and MoS2/FA could remarkably improve the tribological properties of PAO. The nano-MoS2 deposited on the HCl-activated FA presented better lubrication performance than nano-MoS2. It could reduce friction and wear by approximately 27% and approximately 66%, respectively. The lubrication of MoS2/FA can be attributed to the formation of MoS2 and carbon containing lubricating film.

Originality/value

FA was applied as a supporter to prepare MoS2/FA lubricants. The reuse of FA, a solid waste, is important for environmental protection. Moreover, MoS2/FA is more economical than nano-MoS2 as a lubricant, because it contains approximately 71% of low-cost FA.

Details

Industrial Lubrication and Tribology, vol. 75 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 31 January 2023

Zhixiang Li, Shuo Han, Lei Wang and Kunhong Hu

This study aims to investigate the catalytic performance and tribological properties of MoS2 powder.

95

Abstract

Purpose

This study aims to investigate the catalytic performance and tribological properties of MoS2 powder.

Design/methodology/approach

In this work, the authors attempted to use MoS2 nanoparticles (nano-MoS2) as a catalyst to synthesize trimethylolpropane oleate (TMPTO) by esterification of trimethylolpropane and oleic acid. The small amount of highly dispersed nano-MoS2 catalyst remaining in TMPTO needed not to be separated and could be used as a lubricant modifier directly to achieve the purpose of improving the lubricity performance of TMPTO.

Findings

The results demonstrated that nano-MoS2 had good catalytic esterification ability and achieved in situ dispersion of about 0.191% nano-MoS2 in TMPTO while catalyzing the synthesis of base oil. After high-speed centrifugal sedimentation treatment, the product TMPTO still retained about 0.008% of nano-MoS2. The above-synthesized TMPTO has significantly better lubricity performance than commercially available TMPTO, in which the friction coefficient and wear rate could be reduced by 75%.

Originality/value

The results of this study provide an idea for the design of catalysts for ester oil synthesis.

Details

Industrial Lubrication and Tribology, vol. 75 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 26 August 2024

Junjie Gong, Zhixiang Li, Qingqing Lin and Kunhong Hu

This study aims to explore the synthesis and tribological performances of di-n-octyl sebacate (DOS) synthesized with spherical nano-MoS2/sericite (SMS) and carboxylated SMS (CSMS…

14

Abstract

Purpose

This study aims to explore the synthesis and tribological performances of di-n-octyl sebacate (DOS) synthesized with spherical nano-MoS2/sericite (SMS) and carboxylated SMS (CSMS) as catalysts.

Design/methodology/approach

SMS and CSMS were used as esterification catalysts to synthesize DOS from sebacic acid and n-octanol. The two catalysts were in situ dispersed in the synthesized DOS after the reaction to form suspensions. The tribological performances of the two suspensions after 20 days of storage were studied.

Findings

CSMS was more stably dispersed in DOS than SMS, and they reduced friction by 55.6% and 22.2% and wear by 51.3% and 56.5%, respectively. Such results were mainly caused by the COOH on CSMS, which was more conducive to improving the dispersion and friction reduction of CSMS than wear resistance. Another possible reason was the difference between the dispersion amounts of CSMS and SMS in DOS. The sericite of SMS was converted into SiO2 to enhance wear resistance, while that of CSMS only partially generated SiO2, and the rest still remained on the surface to reduce friction.

Originality/value

This work provides a more effective SMS catalytical way for DOS synthesis than the traditional inorganic acid catalytical method. SMS does not need to be separated after reaction and can be dispersed directly in DOS as a lubricant additive. Replacing SMS with CSMS can produce a more stable suspension and reduce friction significantly. This work combined the advantages of surface carboxylation modification and in situ catalytic dispersion and provided alternatives for the synthesis of DOS and the dispersion of MoS2-based lubricant additives.

Details

Industrial Lubrication and Tribology, vol. 76 no. 9
Type: Research Article
ISSN: 0036-8792

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