Experimental research and numerical analysis were applied to study the ultimate load capacity (ULC) and reinforcement of circular-hollow-section N-joint. Four specimens were tested under static load. The ULC of each specimen was obtained and the detailed failure conditions were discussed. Based on the results, both welding a plate on the chord member and filling concrete in the chord member are effective to reinforce the N-joint, but it is suggested that these two methods should not be applied simultaneously. Moreover, considering the four important influence factors of ULC of the joints, the ratio of chord diameter to chord thickness, the ratio of diagonal member diameter to chord member diameter, the axial load on the chord member and the gap size between the two brace members, a new prediction formula of ULC of N-joint was put forward based on numerical analysis results. The new formula was proved to be more accurate than the current Chinese design code in a wide range.

Epoxy resin laminate onto which a pair of copper foil was printed was employed as test samples. The samples were placed in an artificial atmospheric chamber, which was vacuumed by a rotary pump from 100 kPa to 5 kPa. The magnetic field was produced by permanent magnets that were assembled to make E× B drift away from, into and parallel to the sample surface, respectively. Magnetic flux density was adjusted at 120 mT, 180 mT and 240 mT respectively. By applying a negative bias voltage between the electrodes, the time to surface breakdown was recorded. Obtained results show that when E× B is into the surface, the time to the breakdown is shortened; when E× B is away from the surface, the time to the breakdown is delayed; when E× B is parallel to the surface, the time to the breakdown remains approximately the same as the case without magnetic field. With the decrease of pressure, the time to the breakdown increases and the effect of magnetic field on breakdown appears to be strengthened.

A generalized mathematical model of human body current threshold for perception was established and the current flowing through human body could be arbitrary cyclical waveforms. The relationship between human body current threshold for perception and current frequency, true root mean square (RMS) value and influence factor was described. A test system was established based on electroencephalogram (EEG) to study the relationship between human body current threshold for perception and current waveform, frequency and duty cycle so that the data could be obtained objectively and reliably. At least 850 groups of current threshold for perception and 16-lead EEGs were acquired. The theoretical analysis are verified by experimental data, and an amendment proposal on leakage current evaluation limits specified in International Electro-Technical Commission (IEC) standards is suggested.

A fault-tolerant spaceborne mass memory architecture is presented based on entirely commercial-off-theshelf components. The highly modularized and scalable memory kernel supports the hierarchical design and is well suited to redundancy structure. Error correcting code (ECC) and periodical scrubbing are used to deal with bit errors induced by single event upset. For 8-bit wide devices, the parallel Reed Solomon(10, 8) can perform coder/decoder calculations in one clock cycle, achieving a data rate of several Gb/s. In space environment, ECC combined with periodical scrubbing is appropriate and it reduces the word error rate by 5 orders of magnitude with 1% timing overhead and small hardware expenditure.

A novel frequency hopping (FH) sequences generator based on advanced encryption standard (AES) iterated block cipher is proposed for FH communication systems. The analysis shows that the FH sequences based on AES algorithm have good performance in uniformity, correlation, complexity and security. A high-speed, low-power and low-cost ASIC of FH sequences generator is implemented by optimizing the structure of S-Box and MixColumns of AES algorithm, proposing a hierarchical power management strategy, and applying the dynamic clock gating technology based on finite state machine and clock gating. SMIC 0.18 μm standard CMOS technology shows that the scale of ASIC is only about 10.68 kgate, power consumption is 33.8 μW/MHz, and the maximum hop-rate is 1 098 901 hop/s. This design is suitable for portable FH communication system for its advantages in high-security and hop-rate, low-power and low-cost. The proposed FH sequences generator has been employed in Bluetooth SoC design.

To improve global control of disease and reduce global toxicity, a complex seed distribution pattern should be achieved with great accuracy during brachytherapy. However, the interaction between the needle and prostate will cause large deformation of soft tissue. As a result, seeds will be misplaced, sharp demarcation between irradiated volume and healthy structures is unavailable and this will cause side effects such as impotence and urinary incontinence. In this paper, a 3D nonlinear dynamic finite element simulation method with application to robot-assisted image guided brachytherapy is proposed. A magnetic resonance imaging (MRI) based simulation model is built which considers real patient data, nonlinear material property and interaction between the needle and soft tissue. The sensitivities of seed placement error to the needle insertion point, needle orientation and insertion distance are analysed. The result shows that shorter distance between insertion point and target position with compensation in distance can reduce placement error effectively. This method can be used as a complementary instruction for robot-assisted image guided brachytherapy.

Dependent on automatically generated unstructured grids, a comprehensive computational fluid dynamics (CFD)numerical simulation is performed to analyze the influence of nozzle geometry on the internal flow characteristics of a multi-hole diesel injector with the multi-phase flow model based on Eulerian multi-fluid method. The diesel components in nozzle are considered as two continuous phases, diesel liquid and diesel vapor respectively. Considering that both of them are fully coupled and interpenetrated, separate sets of governing equations are established and solved for each phase. The geometric parameters mainly include the length and exit diameter of nozzle, the rounded radius at inlet of nozzle orifice and the angle between axis of injector and axis of nozzle orifice, and they are individually taken into account to analyze the impact on the cavitating flow in nozzle. The results show that the geometrical characteristics of nozzle have a strong influence on the volume fraction of diesel vapor in nozzle and the outlet flow velocity of injector. So cavitation in nozzle orifice should not be neglected for the in-cylinder fuel atomization process, especially for the primary break-up of liquid jet.

Based on experiment modal analysis (EMA) and operation modal analysis (OMA), the dynamic characteristics of cylindrical grinding machine were measured and provided a basis for further failure analysis. The influences of grinding parameters on dynamic characteristics were studied by analyzing the diagnostic signals extracted from racing and grinding experiments. The significant frequency of 38 Hz related to grinding wheel spindle speed of 2 307 r/min showed that the wheel spindle system was in a state of imbalance. And wheel rotating frequency of 38.45 Hz in grinding process was close to the first natural frequency of 38 Hz, which resulted in resonance. Moreover, the main excitation at 147 Hz in grinding process together with resonance led to the deterioration of workpiece. Roundness measurement of workpiece shows good agreement with the vibration responses obtained from dynamic experiments. The fault diagnosis method was also applicable to similar machining systems.

To achieve better cycling performance and vibration comfort of mountain bicycle, the optimization of frame structural parameters and rear suspension scale parameters is investigated based on biomechanics. Firstly, the quadratic sum of rider lower limb muscles stresses is presented as the evaluation criterion of muscle fatigue. By taking the criterion as the objective function, the relative positions of three pivot points of frame are optimized to ensure that the frame structural parameters match the stature of riders. Secondly, the vibration performance is evaluated referring to the ISO 2631-1 Mechanical Vibration and Shock Evaluation of Human Exposure to Whole-Body Vibration. According to this evaluation, the mapping relationship between the vibration performance and rider’s weight as well as structural parameters of rear suspension is revealed. Results show that the length of side link has no significant effect on vibration comfort, while rider’s weight is important in the design of mountain bicycle.

Through the research into the characteristics of 7-DoF high dimensional nonlinear dynamics of a vehicle on bumpy road, the periodic movement and chaotic behavior of the vehicle were found. The methods of nonlinear frequency response analysis, global bifurcation, frequency chart and Poincaré maps were used simultaneously to derive strange super chaotic attractor. According to Lyapunov exponents calculated by Gram-Schmidt method, the unstable region was compartmentalized and the super chaotic characteristic of the nonlinear system was verified. Numerical results by 4-order Runge-Kutta method presented the multiform dynamic behavior of the system.

The hydraulic oscillation of surge tank was analyzed through numerical simulation. A rectangular integral scheme was established in order to improve the numerical model. According to the boundary control equation of surge tank, the rectangular integral scheme omits the second-order infinitesimal and simplifies the solving process. An example was provided to illustrate the rectangular integral scheme, which is compared with the traditional trapezoid integral scheme. Appropriate numerical solutions were gained through the new scheme. Results show that the rectangular integral scheme is more convenient than the trapezoid integral one, and it can be applied to the numerical simulation of various surge tanks in complex pipeline systems.

The hybrid slip model used to generate a finite fault model for near-field ground motion estimation and seismic hazard assessment was improved to express the uncertainty of the source form of a future earthquake. In this process, source parameters were treated as normal random variables, and the Fortran code of hybrid slip model was modified by adding a random number generator so that the code could generate many finite fault models with different dimensions and slip distributions for a given magnitude. Furthermore, a simple method to choose an optimal one from these generated models was proposed. The 1994 Northridge earthquake was taken as an example to demonstrate the procedure of the application of the improved model. Three rock stations, LV3, MCN and PCD, in near-field were used to compare the simulated ground motion from the improved model and optimal model with the observed one. The agreement between them in the periods of interest indicates that the improved model and the method to choose the optimal model are available for the engineering practice of ground motion estimation.

Considering the effects of particle crushing and intermediate principal stress on material yielding strength, the spatial mobilization plane (SMP) yielding criterion and state parameter model including a general critical state line are selected in the analysis of cylindrical cavity expansion. Meanwhile, combining Rowe’s flow rule and Bolton’s simplification to stress-dilatancy relationship to reflect soil shear dilatancy and softening behavior, this paper analyzes the problem of cylindrical cavity expansion in sand by discretizing the plastic zone, which is applicable to cavity expansions from zero initial radius and finite initial radius simultaneously and can determine stress field, strain field and limit cavity pressure. A series of comparative analyses are made with the results ignoring crushing and based on Mohr-Coulomb criterion to examine the effects of crushing as well as the coupled effects of crushing and intermediate principal stress on cavity expansion. Results indicate that crushing causes a reduction in limit cavity pressure and void ratio, and results in less stiff response in expansion curves, the amounts of which increase with initial density and mean effective stress. The consideration of crushing can weaken the effects of intermediate principal stress on expansion, while the consideration of intermediate principal stress makes crushing effects become more prominent. The limit cavity pressure can be reduced by over 40% for dense sand with high initial stress based on SMP criterion when crushing is considered.

The generalized complementarity problem includes the well-known nonlinear complementarity problem and linear complementarity problem as special cases. In this paper, based on a class of smoothing functions, a smoothing Newton-type algorithm is proposed for solving the generalized complementarity problem. Under suitable assumptions, the proposed algorithm is well-defined and global convergent.