This article considers the circumstances in which letters of indemnity(LOI) are usually provided and comments on the use of LOI in relation to the delivery of cargo without surrender of original bills of lading,change...This article considers the circumstances in which letters of indemnity(LOI) are usually provided and comments on the use of LOI in relation to the delivery of cargo without surrender of original bills of lading,changes of destination/deviation,the releasing of clean or wrongly dated bills of lading,the use of switch bills of lading and the commingling of cargoes.The article also comments on the circumstances in which the acceptance of LOI is obligatory and the circumstances in which they can be refused even if offered—an issue which is important given the risks which the acceptance of LOI often entails.Lastly,the article comments on various practical issues which should be borne in mind by those giving or accepting LOI.展开更多
Multiple dominant gear meshing frequencies are present in the vibration signals collected from gearboxes and the conventional spiky features that represent initial gear fault conditions are usually difficult to detect...Multiple dominant gear meshing frequencies are present in the vibration signals collected from gearboxes and the conventional spiky features that represent initial gear fault conditions are usually difficult to detect. In order to solve this problem, we propose a new gearbox deterioration detection technique based on autoregressive modeling and hypothesis testing in this paper. A stationary autoregressive model was built by using a normal vibration signal from each shaft. The established autoregressive model was then applied to process fault signals from each shaft of a two-stage gearbox. What this paper investigated is a combined technique which unites a time-varying autoregressive model and a two sample Kolmogorov-Smimov goodness-of-fit test, to detect the deterioration of gearing system with simultaneously variable shaft speed and variable load. The time-varying autoregressive model residuals representing both healthy and faulty gear conditions were compared with the original healthy time-synchronous average signals. Compared with the traditional kurtosis statistic, this technique for gearbox deterioration detection has shown significant advantages in highlighting the presence of incipient gear fault in all different speed shafts involved in the meshing motion under variable conditions.展开更多
文摘This article considers the circumstances in which letters of indemnity(LOI) are usually provided and comments on the use of LOI in relation to the delivery of cargo without surrender of original bills of lading,changes of destination/deviation,the releasing of clean or wrongly dated bills of lading,the use of switch bills of lading and the commingling of cargoes.The article also comments on the circumstances in which the acceptance of LOI is obligatory and the circumstances in which they can be refused even if offered—an issue which is important given the risks which the acceptance of LOI often entails.Lastly,the article comments on various practical issues which should be borne in mind by those giving or accepting LOI.
基金supported by National Natural Science Foundation of China (Grant No. 50675232)Key Project of Ministry of Education of ChinaChongqing Municipal Natural Science Key Foundation of China (Grant No. 2007BA6021)
文摘Multiple dominant gear meshing frequencies are present in the vibration signals collected from gearboxes and the conventional spiky features that represent initial gear fault conditions are usually difficult to detect. In order to solve this problem, we propose a new gearbox deterioration detection technique based on autoregressive modeling and hypothesis testing in this paper. A stationary autoregressive model was built by using a normal vibration signal from each shaft. The established autoregressive model was then applied to process fault signals from each shaft of a two-stage gearbox. What this paper investigated is a combined technique which unites a time-varying autoregressive model and a two sample Kolmogorov-Smimov goodness-of-fit test, to detect the deterioration of gearing system with simultaneously variable shaft speed and variable load. The time-varying autoregressive model residuals representing both healthy and faulty gear conditions were compared with the original healthy time-synchronous average signals. Compared with the traditional kurtosis statistic, this technique for gearbox deterioration detection has shown significant advantages in highlighting the presence of incipient gear fault in all different speed shafts involved in the meshing motion under variable conditions.
