China is facing challenge of food safety due to that the food consumption for the whole society turns its focus on food quality and safety, while developing economy. This paper, from the angle of developing national food safety strategy and strengthening food safety science and technology, puts forward four priorities for the food safety in China: Firstly, risk analysis is the scientific basis of food safety, and risk assessment is the key technology of food safety, it is suggested to be the first priority of food safety strategy. Secondly, “from farm to table” comprehensive control system is the theoretical basis of food safety technology and practice all along the food chain, which provides the technical assistance for surveillance of food safety. Thirdly, inspection and monitoring technology is the support blocks of alerting, prevention and emergence response, emphasized effort should be taken to exploit a series of rapid detection technology and standardized detection technology for on-line control and lab inspection. Fourthly, the management conception with government, producers and consumers as responsible bodies is the basic principle of food safety, all responsible parties should bear the responsibility for food quality and safety.
The major contradiction faced today for the sustainable development of steel industry lies in the bottleneck of resources and the overburden of environment. In course of speeding-up industrial reshuffle and structural optimization, the enhancing of technological factor provides significant measures to tackle such issues of resources and environment. So, promoting technological progress will become the realistic road to the sustainable development of China's steel industry.
Biomechanical engineering is the important part of the biomedical engineering. It is not only the emerging synthetic subject that makes medicine progress greatly, but also a kind of interdisciplinary subject, which aims to realize treatment, recovery and health care, and then to ensure the health of the people and improve the treating level by using theories and methods of modern biology, medicine, engineering and information science and technology, etc. , to develop new materials, new technologies and new instruments. The contents of this subject include biology, medicine, biomechanics and biorheology, material science, mechanical science, bionics, electronics, computer and information science and control theory, etc. . Based on the above subject, the study, design and manufacture of the relative subjects such as the material for body, artificial internal organ, medical instrument, remote treating system, motion and recovery machine, medical and bionic robot, etc. , are closely related to mechanical engineering. In this paper, viewpoints on research situation, significance, developing tendency and existing problems of biomechanical engineering are presented in order to promote the study of the subject and then put premium on it. On the other hand, with the development of the subject, more applied achievements worthy of popularization can be obtained, which will definitively make maximum economic and social benefits.
At present the main maintenance's manner in the civil aviation field is condition based maintenance which may improve enormously maintenance's efficiency and econmy. Maintenance optimal model concentrates the essence of condition based maintenance and plays an important role in reducing maintenance cost and raising profit of civil aviation corporation. The paper induced the establishing method of several models, such as Delay Time Model and Shock model, Proportional Hazards Model and Markov decision Model, and analyzed these models’ shortcoming in application and prospected their development.
The development of geotechnical plasticity is reviewed and some problems of applying the classic plastic mechanics to geomaterials are analyzed, and then its three hypotheses not fit for the deformation mechanism of geomaterials are pointed out. By giving up the three hypotheses, a generalized plastic potential theory can be obtained from solid mechanics directly, and then the traditional plastic mechanics can be changed to a more generalized plastic mechanics, namely generalized plastic mechanics (GPM). The GPM adopts the component theory as theoretical base, so it can reflect the influence of transition of stress path. The unreasonable phenomena such as excessive dilatancy caused by adopting the normality-flow law can be avoided, and the error caused by the arbitrary assumption of plastic potential surfaces cannot be produced. The yield surface theory, hardening laws and stress-strain relations of GPM are given, and a GPM including the rotation of principal stress axes is also established. It is pointed out that the yield condition is a state parameter as well as a test parameter, and it can only be given by test. After the practical application, it is shown that the GPM can not only be applied to the modeling theory of geomaterials but also to other fields of geomechanics, such as limit analysis.
Seawater desalination provides a new approach to settle the water supply crisis,but a large amount of energy has to be cost during the process of desalination. Each of the several existing methods for seawater desalination has its own advantages and disadvantages, so a combination use of these methods is recommended. The solar heating equipment invented by. Zhang can be used as a good energy source, which is clean and brings no pollution to the environment, for seawater desalination devices.
From the pure extension of the straight bar it can be seen that the balancing stress in the tilted section of the element can only ensure the balance of itself, but can’t ensure the balance of particles on it. The difference between the balance of the element and that of particles on it is demonstrated. A conclusion is drawn that the balancing stress of particles under two dimension stress state is written as σ＇α = σ2x +σ2y+ 2τ2+2τ（σ2x+σ2y）1/2(sinα2 + cosα2))1/2，and the angle between the direction of the balance stress and axis is written as αx= arctan ( τ + (σ2x + σ2y)1/2 sin arctan （σy/σx)) /（τ + （σ2x+σ2y）1/2 cos arctan (σy/σx)). Under two dimension stress state, the principal stress of element and the maximum balancing stress of particles both take place in the 45°diagonal plane, and the balancing stress of particles is 21/2 times that of the principal stress. A new two dimension combining strength condition is derived as σ＇α = (σ2 + 2τ2 + 2στ )1/2≤[σ], and it will replace the formula of bend-torsion combining strength condition of third strength theory ( σ2 + 4τ2)1/2≤[σ] and that of fourth strength theory( σ2 + 3τ2)1/2≤[σ]. A new three dimension combining strength condition is derived as σ＇d =(σ21+σ22+σ23)1/2[σ]and can replace the wrong formula σxd=[((σ1 -σ2)2 +(σ2-σ3)2 +(σ3-σ1)2)/2 ]1/2≤[σ] , which is the corresponding strength formula of the fourth strength theory.
A decoupling control approach based on dynamic inverse system theory has been developed for the bearingless permanent magnet synchronous motor (BPMSM), which is a multi-variable, nonlinear and strong-coupled system. Firstly, inverse system theory is briefly introduced. Secondly, the principle of suspension forces is expounded, and the state equations of torque force and radial suspension forces are set up. Then feasibility of decoupling control based on dynamic inversion theory for BPMSM is discussed in detail, and the dynamic decoupling control arithmetic based on inverse system is deduced. Finally, the simulation results have showed that this kind of control strategy can realize dynamic decoupling control between torque force and radial suspension forces, and the control system has fine dynamic and static performance.
This paper studied on the activation time of sprinkler and the critical heat release rate to activate the sprinkler when a fire happened. By calculation, this paper gave the curve on the activation time and the factors which would impact the activation time. The following conclusions were done： the activation time was almost linear with the installation height and the environment temperature; the fire development mode would affect the increasing rate of the activation time; the exponential relationship was found between the activation time and the response time index (RTI). As the height increased, the critical heat release rate would increase. In order to control fire effectively, the fast response sprinkler must be used when the sprinkler was installed in a high building ceiling.
The paper made an analysis of the similarities and differences about the cryptographic properties of two Boolean functions in the sense of linearly equivalence, and obtained a sufficient and necessary condition about a Boolean function linearly equivalent to some m order correlation-immune Boolean function. It also obtained a sufficient and necessary condition about a Boolean function linearly equivalent to some Boolean function satisfying the k order propagation criterion. Moreover, it showed an example,in which a given Boolean function, that is not correlation-immuned and does not satisfy the propagation criterion can be constructed into a correlation-immuned Boolean function that can satisfy the propagation criterion and is linearly equivalent to the former one.
Based on asymmetric information game and principal-agent theory, by analyzing the forming reasons and connotation relationships of agency costs which occurs during the process of engineering project procurement, this paper gives out the model of best contract and monitor mechanism. It also analyses the relationships between the monitor mechanism and incentive mechanism.
Based on the relation between the incipient yield pressure and the limit of yielding in cylinder according to the elastic disabled rule, a laboratorial method of determining the incipient yield pressure is designed and a set of experimental data were gained. The incipient yield pressure of the cylinder is gained by analyzing the experimental data. The laboratorial method has a good reliability as the experimental value has a little error to the theory value.
The objective of the work was to evaluate the performance of photoelectric and ionic smoke detectors at different flow velocities through the Fire Emulator/Detector Evaluator ( FE/DE). That was accomplished through a series of experiments at different flow velocity, with the same smoldering cottons put directly at the entrance of the FE/DE and in box, respectively. The experiment results indicate that the sensitivity of the two kinds of smoke detectors decreases sharply while the flow velocity around them increases, with the smoldering cottons in the box. However, for the smoldering cottons at the entrance of FE/DE, the sensitivity of the ionic smoke detector does not fall down as sharply as the photoelectric detector. In this case, ionic detectors show better sensitivity than the photoelectric ones. Accordingly, the ionization smoke detector is more suitable for those locations with high flow velocity.
In order to use the non-touch electromagnetic emission (EME) method to better forecast or predict the danger of coal or rock dynamic disaster such as coal or gas outburst, rock or coal outburst and so on, the direction and location of dangerous areas, that is, how to ascertain the monitoring direction and position for EME, is studied. The research results show that according to the computation for the changing rules of EME signals in various directions by means of the coupling equation between EME and stress, and the EME numerical results comparisons for the designated monitored spot, the best monitoring direction and the direction with most stress or maximum dangers can be ascertained. When dynamically monitoring the EME signals in tunnel head-on in the course of tunnel excavation, the monitoring antenna should be laid at the middle height of tunnel and faced with the coal stratum direction. The outburst danger can be monitored by altering the antenna monitoring direction. The available scope of prediction distance can be determined in light of the stress concentration ascertained by numerical simulation for stress field. The EME measuring results on the spot show that it is feasible to study the direction and location of dangerous areas in predicting the danger of coal or rock dynamic disaster by means of the coupling between EME and stress.
In order to resolve crashed accidents caused by fatigue or drowsiness various fatigue detecting algorithms are investigated. Aiming at the needs of large data, high transmission speed and complex operation, a real-time video-based processing system using SAA7.115 as its capture AD, TMS320DM642 as its core, SAA7105 as its display DA ,is designed, and FPGA is used to control the display to achieve advanced function. The system can meet the needs of capture, processing and display of multi-channel video. Furthermore, it can be used as a video and image processing platform.
Because the sludge treating technology is at low level and the phosphorus sludge had polluted the environment seriously, the advantages and shortcomings about some kinds of processes to treat phosphorus sludge are compared in this article. It has put forward a clean and economical process to produce sodium hypophosphite product from phosphorus sludge.
Laser peening forming is an emerging modern process developed from laser shock strengthening. During a laser peening event, pressures well above the dynamic yield strength of the material are imparted to the target in a fraction of nanoseconds. The severity of the loading causes local plastic deformation which ultimately results in the development of the uneven residual stress along the thickness of plate, which pushes the plate to deform. Different parameters of laser can induce different residual stress which make plate achieve different shapes, so controlling technical parameters of laser peening can control the distribution of residual stress, indirectly controlling the deformation of plate to satisfy its design. Laser peening forming is a flexible technology, which can form tight radii in thick material with high accuracy and compressive stress into its surface to extend fatigue lifetime. In the end of the paper, the application prospect of technology is outlined.
This article describes the four generation of reactor types. Firstly, it looks back the development of the 1st. and 2nd. generation reactor types; Secondly, explains the development and the design characteristics of several typical 3rd generation advanced reactor types, and the goals to be reached in the research work for the 4th generation. Finally, it introduces the related situation in China's nuclear power industry.