DYNAMIC THERMAL SHOCK IN A LAYERED CYLINDER WITH INITIALINTERFACE PRESSURE

An analytical method is developed to determine the transient response of dynamic thermostress in a two-layered cylinder with initial interface pressure. At first, the initial interface pressure in a two-layered cylinder caused by a heat-assembling method is considered as the initial condition of a thermal elastodynamic equilibrium equation. Thus, a thermal elastodynamic solution for a separate hollow cylinder with the initial stress field is found out by means of a series of simply mathematical transform. By making use of the boundary conditions and continuity conditions of a layered cylinders, the solution for the thermal shock exerting an influence on the initial interface pressure in a two-layered cylinder is also discussed.

Molecular dynamics study of thermal stress and heat propagation in tungsten under thermal shock

Using molecular dynamics （MD） simulation, we study the thermal shock behavior of tungsten （W）, which has been used for the plasma facing material （PFM） of tokamaks. The thermo-elastic stress wave, corresponding to the collective displacement of atoms, is analyzed with the Lagrangian atomic stress method, of which the reliability is also analyzed. The stress wave velocity corresponds to the speed of sound in the material, which is not dependent on the thermal shock energy. The peak pressure of a normal stress wave increases with the increase of thermal shock energy. We analyze the temperature evolution of the thermal shock region according to the Fourier transformation. It can be seen that the “obvious” velocity of heat propagation is less than the velocity of the stress wave; further, that the thermo-elastic stress wave may contribute little to the transport of kinetic energy. The heat propagation can be described properly by the heat conduction equation. These results may be useful for understanding the process of the thermal shock of tungsten.

Performance of a double-layer BAF using zeolite and ceramic as media under ammonium shock load condition

An experiment was carried out to investigate the anti-ammonium shock load capacity of a biological aerated filter （BAF） composed of a double-layer bed. This bed was made up of a top layer of ceramic and a bottom layer of zeolite. The experiment shows that the anti-ammonium shock load process can be divided into two processes： adsorption and release. In the adsorption process, the total removal efficiency of ammonia nitrogen by zeolite and ceramic was 94%. In the release process, the ammonia nitrogen concentration increased significantly and then gradually returned to the normal level four hours after the shock load. The results indicated that the double-layer BAF had a high level of adaptability to the short-term ammonium shock load and long-term operation. The main factors influencing the dynamic process of ammonia nitrogen adsorption were the filter bed height, ammonia nitrogen concentration of influent, and flow rate. The bed depth service time （BDST） model was used to predict the relationship between the filter bed height and breakthrough time at different flow rates, and the results are reliable.

Numerical study of detonation shock dynamics using generalized finite difference method

The generalized finite difference method (GFDM) used for irregular grids is first introduced into the numerical study of thelevel set equation, which is coupled with the theory of detonation shock dynamics (DSD) describing the propagation of thedetonation shock front. The numerical results of a rate-stick problem, a converging channel problem and an arc channel prob-lem for specified boundaries show that GFDM is effective on solving the level set equation in the irregular geometrical domain.The arrival time and the normal velocity distribution of the detonation shock front of these problems can then be obtainedconveniently with this method. The numerical results also confirm that when there is a curvature effect, the theory of DSDmust be considered for the propagation of detonation shock surface, while classic Huygens construction is not suitable anymore.

Instantaneous stress release in fault surface asperities during mining-induced fault-slip

Fault-slip taking place in underground mines occasionally causes severe damage to mine openings as a result of strong ground motion induced by seismic waves arising from fault-slip. It is indicated from previous studies that intense seismic waves could be generated with the shock unloading of fault surface asperities during fault-slip. This study investigates the shock unloading with numerical simulation. A three-dimensional （3D） numerical model with idealized asperities is constructed with the help of discrete element code 3DEC. The idealization is conducted to particularly focus on simulating the shock unloading that previous numerical models, which replicate asperity degradation and crack development during the shear behavior of a joint surface in previous studies, fail to capture and simulate. With the numerical model, static and dynamic analyses are carried out to simulate unloading of asperities in the course of fault-slip. The results obtained from the dynamic analysis show that gradual stress release takes place around the center of the asperity tip at a rate of 45 MPa/ms for the base case, while an instantaneous stress release greater than 80 MPa occurs near the periphery of the asperity tip when the contact between the upper and lower asperities is lost. The instantaneous stress release becomes more intense in the vicinity of the asperity tip, causing tensile stress more than 20 MPa. It is deduced that the tensile stress could further increase if the numerical model is discretized more densely and analysis is carried out under stress conditions at a great depth. A model parametric study shows that in-situ stress state has a significant influence on the magnitude of the generated tensile stress. The results imply that the rapid stress release generating extremely high tensile stress on the asperity tip can cause intense seismic waves when it occurs at a great depth.

Modal analysis and pulse response of mobile hard disk head actuator arm assembly

Head actuator arm assembly (HAA) is the most important mechanical component of a mobile hard disk drive (HDD) and its shock dynamic response is a principal index of vibration resistance. In this paper,a finite element (FE) model is firstly developed in ANSYS of 2.5 inch (1 inch=25.4 mm) mobile hard disk. This model includes actuator arm,voice coil motor (VCM) and pivot bearing. The various step modal of HAA is calculated by FE model. Then the actuator arm vibration behavior is simulated with LS-DYNA procedure. The influence of pulse waveform,pulse amplitude and pulse width on the shock response of the relative displacement of the head actuator arm assembly is studied.

A Novel Porcine Model of Septic Shock Induced by Acute Respiratory Distress Syndrome due to Methicillin-resistant Staphylococcus aureus

Background： Sepsis is one of the main canses of mortality in critically ill patients following progression to septic shock. To investigate the pathophysiologic changes of sepsis, we developed a novel porcine model of septic shock induced by acute respiratory distress syndrome （ARDS） due to methicillin-resistant Staphylococcus aureus （MRSA） pneumonia. Methods： Twenty-six male Landraces （Lvyuanweiye, Beijing, China） weighing 30 - 2 kg were divided into lbur groups： sham gronp （SH： n = 5）; cotton smoke inhalation group （SM; n = 6）; MRSA pneumonia group （MR; n = 6）; and septic shock group with cotton smoke inhalation ＋ MRSA pneumonia （SS; n = 9）. Extensive hemodynamics, oxygen dynamics, and lung function were monitored for 24 11 following the injury or until death. Tissues were collected, and histopathology evaluations were carried out. Results： Blood cultures from 6 of 9 animals in the SS group were positive for MRSA. Two hours following the injury, decreased mean arterial blood pressure （60 70 mmHg） and cardiac index （〈2 L-rain -＇m --） were observed in the animals in the SS group, while systemic vascular resistance index was increased. The hemodynamic characteristics of septic shock were only observed in the SS group but not significant in the other groups, The PO_JFiO2 in the SM and SS groups decreased to 300 and 100, respectively. In the SS group, extravascular lung water index increased to 20 ml/kg, whereas thoracopulmonary compliance decreased to 10 ml/H2O after injury. Deterioration of pulmonary function in the SS group was more serious than the SM and MR groups. Severe lung injury in the SS group was confinaaed by the histopathology evaluations. The lung injury confirmed by high-resolution thin-section computed tomography and histopathology in the SS group was more serious than those of other groups. Conclusions： In the present study, we developed a novel porcine model of septic shock induced by ARDS due to severe MRSA pneumonia with characteristic hyperdynamic and hypodynamic phases in 24 h, which mimicked the hemodynamic changing of septic shock in human.

Comparative Study on Two Melting Simulation Methods:Melting Curve of Gold

Melting simulation methods are of crucial importance to determining melting temperature of materials efficiently.A high-efficiency melting simulation method saves much simulation time and computational resources.To compare the efficiency of our newly developed shock melting(SM)method with that of the well-established two-phase(TP)method,we calculate the high-pressure melting curve of Au using the two methods based on the optimally selected interatomic potentials.Although we only use 640 atoms to determine the melting temperature of Au in the SM method,the resulting melting curve accords very well with the results from the TP method using much more atoms.Thus,this shows that a much smaller system size in SM method can still achieve a fully converged melting curve compared with the TP method,implying the robustness and efficiency of the SM method.