Objective
To analyze sleep change characteristics of long haul stationed escort helicopter flying personnel by investigating their sleeping states on different ships in different stage of voyage and to sum up the countermeasures.
Methods
We selected 47 escort helicopter flying personnel as the subjects, including 10 flying personnel based on frigate, 17 flying personnel based on landing craft, and 20 land-based flying personnel. We used a sleep questionnaire in clinic (self-rating scale of sleep, SRSS) to investigate sleep qualities of the flying personnel on different ships in different stage of voyage. By comparing with land-based flying personnel and national normal model, we analyzed sleep change characteristics of long haul stationed escort helicopter flying personnel.
Results
Till to 7 d and 78 d on ship, SRSS total scores of the flying personnel were 22.27±4.40 and 21.56±4.40 respectively, which were statistically higher than those of land-based flying personnel (P<0.01). Ten scores of sleep factors of flying personnel for 78 d stationed on ship were respectively compared with those of land-based flying personnel. In spite of early awaking, drug dose and nightmare regression factors, the other 7 factors had statistically higher than those of land-based flying personnel (P<0.05, P<0.01). Score of sleep time factor was 2.63±0.56, that was higher than national normal model (P<0.01).
Conclusions
Sleep quality of the escort flying personnel stationed on ship for a long time is significantly impacted as compared with that of the land-based flying personnel. It is suggested that more attention should be paid on sleep problems of the flying personnel stationed on ship for a long time, and health care and flight medical examination should be enhanced. Meanwhile, sleep model of military flying personnel should be developed to improve the scientificity and effectiveness of evaluation.
Key words:
Sleep; Sleep initation and maintenance disorders; Naval medicine; Aircrews
Magnetic refrigeration has become a promising new technology to replace conventional vapor-compression refrigeration technology, for it has excellent application characteristics such as the high efficiency, environmental friendliness and structural simplicity. Many studies have been carried out to analyze the various subsystems, but the interaction laws between the systems are not yet clear, and the optimization of each subsystem is still an area of research worth exploring. This work is based on a compact room temperature magnetic refrigeration system developed before, and carries out experimental research on the different flow time ratio to explore the correlation among refrigeration temperature span, cooling capacity, pressure drop, coefficient of performance (COP) and blow fraction under a fixed magnetic field timing. Especially, the effects of different flow time ratios (100%, 80%, 60%) on the system performance are studied under magnetic field timing of 1∶4∶1∶4 and a frequency of 0.45 Hz. The experimental results reveal that a low utilization factor combined with a high flow time ratio can achieve a greater temperature spread, whereas a high utilization factor combined with a high flow time ratio can accomplish a bigger cooling capacity. When the utilization factor is 0.42 and the flow time ratio is 100%, the maximum unloaded cooling temperature span is 26.2 K. Meanwhile, the effects of the utilization factor and flow time ratio on the pressure drop and COP of the regenerator are studied in detail. It is discovered that raising the flow time ratio and reducing the utilization factor both result in a fall in fluid velocity, which leads the pressure to further decrease and the COP to rise. In a word, this research investigates the relationship among cooling temperature span, cooling capacity, pressure drop, COP, and flow time ratio in a fixed magnetic field timing, thus providing the groundwork for future improving the performances of room temperature magnetic refrigeration systems.
In this paper, a new piece-wise fast alignment method for SINS stationary alignment is proposed. First of all, the fine horizontal alignment is executed. After the fine horizontal alignment, using the output angle velocity of the gyros, we can calculate the azimuth misalignment angle in high speed. Theoretical analysis as well as the simulation result indicate: Compared with the method using Kalman filter in the whole process of the alignment, the piece-wise fast alignment method has the same steady-state accuracy,but in the process of the fine azimuth alignment, the mechanical arrangement of SINS is not needed and the computational complexity is reduced. The time of fine alignment can be shortened to 60 seconds or so. This method makes up the defect that the convergence of the azimuth misalignment angle is slow, accelerates the initial alignment process and has an important practical value.
In perovskite EuTiO3, the flexibility to regulate the magnetic characteristics and magnetocaloric effect (MCE) by switching magnetic from antiferromagnetic to ferromagnetic. In the present work, a series of Eu(Ti,Nb,Mn)O3 compounds, abbreviated as ETNMO for convenience of description, were fabricated and their crystallography, magnetism together with cryogenic magnetocaloric effects were systematically investigated. The crystallographic results demonstrate the cubic perovskite structure for all the compounds, with the space group of Pm3m. Two magnetic phase transitions have been observed in these second-order phase transition (SOPT) materials. The joint substitution of elements Mn and Nb can considerably manipulate the magnetic phase transition process and magnetocaloric performance of the ETNMO compounds. As the Mn content increases, gradually widened -ΔSM-T curves are obtained, and two peaks with a broad shoulder are observed in the -ΔSM-T curves for ΔH≤1 T. Under a field change of 0-5 T, the values of maximum magnetic entropy change (-ΔSmax M) and refrigeration capacity (RC) are evaluated to be 34.7 J·kg-1·K-1 and 364.9 J·kg-1 for EuTi0.8625Nb0.0625Mn0.075O3, 27.8 J·kg-1·K-1 and 367.6 J·kg-1 for EuTi0.8375Nb0.0625Mn0.1O3, 23.2 J·kg-1·K-1 and 369.2 J·kg-1 for EuTi0.8125Nb0.0625Mn0.125O3, 17.1 J·kg-1·K-1 and 357.6 J·kg-1 for EuTi0.7875Nb0.0625Mn0.15O3, respectively. The considerable MCE parameters make the ETNMO compounds potential candidates for cryogenic magnetic refrigeration.
Abstract A rare earth oxyborate crystal K 2 Nd 2 O(BO 3 ) 2 has been grown by means of high temperature solution method for the first time. It crystallizes in monoclinic P 2 1 / c (No. 14) space group, and the lattice parameters are a =11.318(6) Å, b =6.575(4) Å, c =10.689(6) Å, β =117.062(12)°, and Z =4. The absorption spectrum, emission spectrum, and fluorescence lifetime of K 2 Nd 2 O(BO 3 ) 2 have been evaluated, and the foundational spectral parameters have been analysed according to the Judd‐Ofelt theory. The high concentration of activated ions (1.13×10 22 ions/cm 3 ), large absorption coefficient (87.63 cm −1 ), long fluorescence lifetime (91.2 μs), and large emission cross section (2.03×10 −20 cm 2 ) of K 2 Nd 2 O(BO 3 ) 2 suggest its potential applications of microchip lasers.
A suitable coherent description of the reversible and irreversible magnetic entropy changes in a Tb-based metallic glass with strong random magnetic anisotropy (RMA) is presented. A giant irreversible positive magnetic entropy change is observed from magnetic measurements at low temperatures, which is found to arise from the entropy production, while a small negative one is obtained from heat capacity measurements. The temperature dependences of the irreversible positive magnetic entropy change under a field change of 5 T and the internal entropy production in the initial magnetization process can be described by an exponential law, which is determined by RMA.
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