Dynamic Response and Injury Prediction for Lumbar Vertebrae of Pilots with Spondylolysis under Persistent Overload / 医用生物力学

Objective Based on construction and verification of the lumbar finite element model, the simulation calculation and injury prediction on dynamic response of normal lumbar model and L5 unilateral and bilateral spondylolysis models of the pilot were carried out, so as to explore the influence of persistent flight overload on normal and spondylolysis lumbar vertebrae of the pilot. Methods The precise finite element model of lumbavertebrae was established using reverse engineering software and computer-aided engineering (CAE) technology based on CT images. The validity of the lumbar vertebrae model was verified by static and dynamic in vitro experiments. The biomechanical simulation analysis on normal and spondylolysis lumbar vertebrae of the pilotunder persistent overload was carried out, and the spinal injury was predicted and analyzed by dynamic response index (DRI) injury evaluation and prediction method. Results The maximum isthmus stress of L5 vertebra in unilateral and bilateral spondylolysis models were 105. 29 MPa and 126. 32 MPa, respectively, which were significantly higher than those in normal model. The L4-5 and L5-S1 intervertebral discs of the spondylolysis model were more prone to premature degenerative changes than those of normal model. Combined with DRI spinal injury prediction method, the probability of spinal injury in normal lumbar vertebrae, lumbar vertebrae with L5 unilateral and bilateral spondylolysis were 0. 001 4% , 2. 26% and 3. 21% , respectively, and the probability of spinal injury was significantly increased after the occurrence of spondylolysis. Conclusions The spondylolysis increases the load of lumbar isthmus under flight overload. The results provide more accurate data support for the formulation of training programs and the development of protective devices to ensure flight safety

Dynamic Response Simulation and Damage Prediction of Pilot Cervical Vertebra During Maneuver Flight / 医用生物力学

Objective To simulate dynamic response of cervical spine of the pilot during typical maneuver flight movements using finite element method, as well as make analysis and prediction on damage failure of the pilot neck during flight by impact injury and fatigue injury model of biological tissues.Methods A geometrically accurate finite element model of the neck was constructed, and validity of the model was verified by relevant examples. Then, the acceleration curves of centrifugal trainer under different modes were loaded for numerical simulation, and impact injury and fatigue injury of tissues were predicted by using the universal cervical injury criterion and the fatigue damage model of biological tissues.Results The maximum stress of the vertebrae and intervertebral disc caused by overload impact was 66.53 MPa and 58.63 MPa respectively during typical maneuver flight. According to the Nij injury criteria, the maximum Nij was 0.096, which was lower than the injury tolerance threshold of 1, and would not cause direct acute injury to cervical tissues. Based on fatigue damage model of biological tissues, it was found that cancellous bone suffered fatigue failure under the condition of uninterrupted repeated loading for more than 40 000 times. Considering the limited flight career of the pilot, the vertebral tissues would not be fractured due to the accumulation of fatigue damage.Conclusions To a certain extent, the results can contribute to formulating pilot training and flight plans, and also provide data support for the development of its protective equipment.

Efficient connectivity analysis of electroencephalogram in the pre-shot phase of rifle shooting based on causality method / 生物医学工程学杂志

The directed functional connectivity in cerebral cortical is the key to understanding the pattern of the behavioral tissue. This process was studied to explore the directed functional network of rifle shooters at cerebral cortical rhythms from electroencephalogram (EEG) data, aiming to provide neurosciences basis for the future development of accelerating rifle skill learning method. The generalized orthogonalized partial directed coherence (gOPDC) algorithm was used to calculate the effective directed functional connectivity of the experts and novices in the pre-shot period. The results showed that the frontal, frontal-central, central, parietal and occipital regions were activated. Moreover, the more directed functional connections numbers in right hemispheres were observed compared to the left hemispheres. Furthermore, as compared to experts, novices had more activated regions, the stronger strength of connections and the lower value of the global efficiency during the pre-shot period. Those indirectly supported the conclusion that the novices needed to recruit more brain resources to accomplish tasks, which was consistent with "neural efficiency" hypothesis of the functional cerebral cortical in experts.

Analysis of young male anthropometric parameters for design of driving and operations in cars / 生物医学工程学杂志

Fitting formulas of typical parameters were obtained through analysis of anthropometric parameters of armored car driver and operators. These formulas could be a basis for design of product and equipment of cars, cumulating and updating of basic data of similar sample and edition of relative standards. 76 anthropometric static parameters and 11 functional parameters were chosen, and 1 243 soldiers with armored forces were chosen to be tested. The correlation and fitting formulas of body height, sitting height and other parameters were measured and obtained. We also contrasted measured data with data from GJB1835-1993. The present analysis showed that the correlation between sizes of body length and body height and sitting height was significant. Sizes of body length and enclose size and width direction were all increased compared to those in the 1980s. The present results were consistent with other researchers' current research results. The measured data could be an important basis for the data of young male anthropometric parameters and edition of relative standards and design of specific equipment.

Different Characteristics of Heart Rate Variability in Mental and Physical Fatigue States / 航天医学与医学工程

Objective Using heart rate(HR) and heart rate variability(HRV) as stress level indices,to find out the changes of stress level in mental fatigue and physical fatigue,respectively.Methods The changes of HR and HRV during reading task and written calculation task were studied in mental fatigue,and the change of HR during exhausting physical exercise was analyzed in physical fatigue.Results Subjects showed high stress level as heavy mental load was imposed on at the beginning of the experiment.Decreased HR and increased HRV caused by physiological inhibitory protection,indicating an increased mental fatigue level,showed that mental fatigue level was opposite to mental stress level under heavy mental workload.The phenomenon that HR increased along with the physical fatigue level increasing,proved that physical fatigue degree was often consistent with physical stress level,which revealed the compensative adjustment.Conclusion The significant difference of autonomic nervous system(ANS) activity between mental fatigue and physical fatigue,may be explained by the difference between mental stress and physical stress of mechanism,mainly born organ and workload intensity.

Influence of Multi-factors on Fatigue Evaluation of Typical upper Extremity Operation / 航天医学与医学工程

Objective To study the influences of 8 important factors on fatigue evaluation as performing typical upper extremity operation. Methods Thirty-two subjects were divided into young male (G1),mid-age male (G2) and female (G3) groups. They were required to perform right arm flex/extend operation under different situations for 16 runs. L16 (44?23) orthogonal array was used to combine different situations (factors). Brief fatigue inventry(BFI) were recorded and simultaneous manual works (energy) were calculated. Both of them were used to evaluate the operation strategies. Results Difference between G1 and G2 was not significant,whereas it was as large as 39%,between G1+G2 and G3 (P

Review on Body Fatigue Assessment of Human Operation / 航天医学与医学工程

The human workload is of great importance to ergonomic evaluation of man-machine system.The local muscle fatigue is considered to be one of the main indexes.In this paper,the cause of local muscle fatigue,its assessment methods and development trends were described in detail.Some related technological problems about its mechanism,measurement and assessment methods were analyzed and induced.Finally,some views were put forward for discussion.

Research on Effect Factors to Function of Human-machine System as Displaying with LCD / 航天医学与医学工程

Objective To provide the experimental data for standard establishment and ergonomics research on manned spaceflight displays basing on relation of six effect factors to function of human-machine system as displaying with LCD,and the best factor-level-composition is chosen.Methods An experimental system was developed.The orhoganal experiment means was adopted.Twenty subjects were asked to finish three tasks: to view parameters of the whole screen interface,to seek local parameters,to identify the fault events quickly.Three indices: reaction time,error times and times of unable to recognize were analyzed.Results The indices were much different for different factors at different levels.According to the indices of mean reaction time,extreme difference of view-angle was the lowest and view-distance the highest.Conclusion The order of the display effects of different factors on human-machine system is successively: viewdistance,illuminant level,character height,color of character/background and viewangle.

Simulation Study on Performance of Control by Man and Machine in the Stage of Final Approaching for Rendezvous and Docking / 航天医学与医学工程

Objective To study the performance evaluation of integration rendezvous and docking(RVD)control by man and machine in order to provide reference for function allocation between man and machine.Method By a rendezvous and docking experimental system,30 male volunteers aged 20～40 took part in the performance evaluation experiments.The RVD integration control success rates and total thruster ignition time were chosen as evaluation indices.Result The experiment showed that if less than three RVD parameters control tasks were completed by the subjects and the rest of parameters control task completed by automation,the RVD success rate would be larger than 80.47% and the fuel consumption would be optimized.In addition,there were ten subjects who finished the whole 6 RVD parameters control tasks by enough train.Conclusion If the astronauts role should be integrated into the RVD control,it is suitable for them to finish the heading,pitch and roll control in order to assure the man-machine system high performance.When astronauts were needed to finish all parameters control,two points should be taken into consideration,enough fuel and unconstraint operation time.