ABSTRACT
Intelligent operation and maintenance technology for vessels can ensure the safety of the entire system, especially for the development of intelligent and unmanned marine technology. The material properties of metal abrasive particles in oil could demonstrate the wear areas of the marine mechanical system because different components consist of different materials. However, most sensors can only roughly separate metallic contaminants into ferromagnetic and non-ferromagnetic particles but cannot differentiate them in greater detail. A micro-three-coil sensor is designed in this paper; the device applies different excitation signals to two excitation coils to differentiate materials, based on the different effects of different material particles in the asymmetric magnetic field. Therefore, a particle's material can be judged by the shape of the induction electromotive force output signal from the induction coil, while the particle size can be judged by the amplitude of the signal. Experimental results show that the material differentiation of four different types of particles can be achieved, namely, of aluminum, iron, 304 stainless steel, and carbon steel. This newly designed sensor provides a new research prospect for the realization of an inductive detection method to distinguish non-ferrous metals and a reference for the subsequent detection of metal contaminants in oil and other liquids.
ABSTRACT
Spices are widely used in daily life such as diet and have certain activity. Especially in China, spices have been mainly used as condiments for thousands of years in order to improve the sensory quality of food; in addition, they and their derivatives can also be used as preservatives. In this study, three spices with unique Chinese characteristics widely used were selected: cassia bark (bark of Cinnamomum camphora Presl), bay fruits (Laurus nobilis), and cloves (Syzygiumaromaticum). The main components and antibacterial ability of these three spices were analyzed by simulated extraction method. Through headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) analysis, it was determined that the main active compounds in the essential oils of cassia bark, bay fruits and cloves were cinnamaldehyde (78.11%), cinnamaldehyde (61.78%) and eugenol (75.23%), respectively. The agar plate diffusion test and the simulated food culture medium experiment confirmed that the essential oils extracted from the three flavors have antibacterial effects on Listeria monocytogenes, Listeria innocua, Listeria welshimeri, Listeria ivanovii, Listeria grayi and Vibrio parahaemolyticus. The antibacterial activity of different strains has different optimal extraction conditions. Generally speaking, cinnamon essential oil has the strongest antibacterial activity, while laurel fruit has the lowest antibacterial activity. The study proved the antibacterial activity of these three Chinese-specific spices and provided some new ideas and methods for the subsequent research and preparation of natural food additives and food antibacterial agents.
