足球守门员门前封锁和控制——“出击”的探讨

守门员在门前采取攻击性的出击 ,大范围封锁和控制罚球区的地面和空间 ,是稳固球门 ,瓦解对方进攻的有力武器 .本文从守门员出击的个性心理特征、封堵选位。

足球守门员“出击”战术能力评价

“出击”能力是守门员战术能力的重要内容之一 ,并且能够较好地反映守门员控制罚球区的防守能力 .因此 ,本文主要从定性评价和定量评价两个方面介绍如何制定守门员“出击”战术能力的评价方法和要求 ,目的在于探索科学的评定守门员战术能力的方法 。

Effect of an Asymmetric Doping Channel on Partially Depleted SOI MOSFETs

Asymmetric doping channel （AC） partially depleted （PD） silicon-on-insulator （SOI） devices are simulated using two-dimensional simulation software. The electrical characteristics such as the output characteristics and the breakdown voltage are studied in detail. Through simulations,it is found that the AC PD SOI device can suppress the floating effects and improve the breakdown characteristics over conventional partially depleted silicon-on-insulator devices. Also compared to the reported AC FD SOI device,the performance variation with device parameters is more predictable and operable in industrial applications. The AC FD SO1 device has thinner silicon film, which causes parasitical effects such as coupling effects between the front gate and the back gate and hot electron degradation effects.

DCFl-Checker： Checking Kernel Dynamic Control Flow Integrity with Performance Monitoring Counter

It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an ＂attachment＂ in each control transfer. However, the attachment introduces additional cost except performance penalty. For example, the attachment must be unique or restrictedly modified. In this paper, we propose a novel approach to detect integrity of dynamic control flows by counting executed branch instructions without involving any attachment. Our solution is based on the following observation. If a control flow is compromised, the number of executed branch instructions will be abnormally increased. The cause is that intruders usually hijack control flows for malicious execution which absolutely introduces additional branch instructions. Inspired by the above observation, in this paper, we devise a novel system named DCFI- Checker, which detect integrity corruption of dynamic control flows with the support of Performance Monitoring Counter （PMC）. We have developed a proof-of-concept prototype system of DCFI-Checker on Linux fedora 5. Our experiments with existing kemel rootkits and buffer overflow attack show that DCFI- Checker is effective to detect compromised dynamic control transfer, and performance evaluations indicate that performance penaltyinduced by DCFI-Checker is acceptable.

The stress state of geological structure and mining dynamic disaster in Fuxin basin

Further evidences show that most mining dynamic disasters are mainly oc- curred nearby NNE and near SN geological structures.In-situ stress measurement in Fuxin basin shows that the orientation of major compressed stress is near EW.At this stress field,geological structures with deferent strike have deferent stress state and dis- place mode.NNE and near SN geological structures are compressed to thrust and come into being high stress zone.NWW and NEE geological structures are tensile to separate and not prone to being low stress zone.NW structure is intervenient of them.So NEE and near SN structures are easy to occurre mining dynamic disasters and NWW and NEE structures is 'safety' comparatively.The mining dynamic disaster is controlled by stress state of geologic structure,which is determined by its strike.

Analysis of mechanism of shock bump due to roof fall

According to the characteristics of the shock bump due to roof fall, a simple mechanics model has been established by applying the catastrophic theory and the law of energy conservation. The author suggests that the shock bump may be induced by the sudden energy release in the roof falling after underground mineral extractions, and through the systematic analysis of actual examples on site, the empirical formulae for the roof falling and energy release are derived, which would provide a new way for the study of the origin and mechanism of mine tremor due to fallen-in roof structure. It is of a great importance to enrich the shock bump theory and production safety in mine.

Properties of AA7075 aluminum alloy in aging and retrogression and reaging process

A retrogression process was applied to AA7075alloy at180,240and320°C for1,30,50,70,90and120min.After the retrogression,aging treatment was reapplied with T6conditions(120°C,24h).The mechanical properties of aged samples were determined by V-Charpy and hardness tests and also,physical properties of samples were determined by electrical conductivity tests.Moreover,microstructural properties were characterized by light microscope and transmission electron microscope.The results show that the effects of the temperature and the duration of the retrogression and reagent on the impact toughness and hardness are related to the precipitates at the grain boundary.

Propagation law of shock waves and gas flow in cross roadway caused by coal and gas outburst

In order to study the propagation law of shock waves and gas flow during coal and gas outburst,we analyzed the formation process of outburst shock waves and gas flow and established the numerical simulation models of the roadways with 45°intersection and 135°intersection to simulate the propagation of outburst gas flow and the process of gas transport.Based on the analysis of the simulation results,we obtained the qualitative and quantitative conclusions on the characteristics and patterns of propagation and attenuation of outburst shock waves and gas flow.With the experimental models,we investigated the outburst shock waves and gas flow in the roadways with the similar structures to the simulated ones.According to the simulation results,when the angle between the driving roadway and the adjacent roadway increased,the sudden pressure variation range in adjacent roadway and the influencing scope of gas flow increased and the sudden pressure variation duration decreased.The intersection between the driving roadway and the adjacent roadway has no effect on airflow reversal induced by the shock waves and gas flow.

New State Recovery Attacks on the Grain v1 Stream Cipher

The Grain v1 stream cipher is one of the seven finalists in the final e STREAM portfolio. Though many attacks have been published,no recovery attack better than exhaustive key search on full Grain v1 in the single key setting has been found yet. In this paper,new state recovery attacks on Grain v1 utilizing the weak normality order of the employed keystream output function in the cipher are proposed. These attacks have remarkable advantages in the offline time,online time and memory complexities,which are all better than exhaustive key search. The success probability of each new attack is 0.632. The proposed attack primarily depends on the order of weak normality of the employed keystream output function. This shows that the weak normality order should be carefully considered when designing the keystream output functions of Grain-like stream ciphers.

Silicon light emitting device in CMOS technology

A novel silicon light emitting device was realized with standard 0.35μm 2P4M Mixed Mode/RF CMOS technology. The device functions in a reverse breakdown mode and can be turned on at 8.3 V and operated normally at a wide voltage range of 8.3 V-12.0 V. An output optical power of 13.6 nW was measured at the bias of 10 V and 100 mA, and the emitted light intensity was calculated to be more than 1 mW/cm2. The optical spectrum of the device is in the range of 500-820 nm.

Numerical simulation for propagation characteristics of shock wave and gas flow induced by outburst intensity

In order to analyze the propagation characteristics of shock wave and gas flow induced by outburst intensity, the governing equations of shock wave and gas flow propagation were put forward, and the numerical simulation boundary condition was obtained based on outburst characteristics. The propagation characteristics of shock wave and gas flow were simulated by Fluent software, and the simulation results were verified by experiments. The results show that air shock wave is formed due to air medium compressed by the transient high pressure gas which rapidly expands in the roadway; the shock wave and gas flow with high velocity are formed behind the shock wave front, which significantly decays due to limiting effect of the roadway wall. The attenuation degree is greater in the early stage than that in the late stage, and the velocity of gas convection transport is lower than the speed of the shock wave.The greater the outburst intensity is, the greater the pressure of the shock wave front is, and the higher the speed of the shock wave and gas flow is.

A Practical Online Approach to Protecting Kernel Heap Buffers in Kernel Modules

Heap overflow attack is one of the major memory corruption attacks that have become prevalent for decades. To defeat this attack,many protection methods are proposed in recent years. However,most of these existing methods focus on user-level heap overflow detection. Only a few methods are proposed for kernel heap protection. Moreover,all these kernel protection methods need modifying the existing OS kernel so that they may not be adopted in practice. To address this problem,we propose a lightweight virtualization-based solution that can protect the kernel heap buffers allocated for the target kernel modules. The key idea of our approach is to combine the static binary analysis and virtualization technology to trap a memory allocation operation of the target kernel module,and then add one secure canary word to the end of the allocated buffer. After that,a monitor process is launched to check the integrity of the canaries. The evaluations show that our system can detect kernel heap overflow attacks effectively with minimal performance cost.

Study on the formation mechanism of shock wave in process of coal and gas outburst

According to the research results of motion parameters of coal-gas flow,analyzedthe formation mechanism of shock waves at different states of coal-gas flow in theprocess of coal and gas outburst,and briefly described the two possible cases of outburstshock wave formation and their formation conditions in the process of coal and gas out-burst,and then pointed out that a high degree of under-expanded coal-gas flow was themain reason for the formation of a highly destructive shock wave.The research resultsimproved the shock wave theory in coal and gas outburst.

Injection and Extraction Techniques in Circular Accelerators

Injection and extraction are usually the key systems in circular accelerators.They play important roles in transferring the beam from one stage acceleration to the other or to experimental stations.It is also in the injection and extraction regions where beam losses happen mostly.Due to the tight space and to reduce the perturbation to the circulating orbit,the devices are usually designed to meet special requirements such as compactness,small stray field,fast rise time or fall time,etc.Usual injection and extraction devices include septum magnets,kicker magnets, electrostatic deflectors,slow bump magnets and strippers.In spite of different accelerators and specification for the injection and extraction devices,many techniques are shared in the design and manufacturing.This paper gives a general review on the techniques employed in the major circular accelerators in China.

Low-carbon advanced nanostructured steels:Microstructure, mechanical properties, and applications

Low-carbon advanced nanostructured steels have been developed for various structural engineering applications, including bridges, automobiles, and other strength-critical applications such as the reactor pressure vessels in nuclear power stations. The mechanical performances and applications of these steels are strongly dependent on their microstructural features. By controlling the size,number density, distribution, and types of precipitates, it is possible to produce nanostructured steels with a tensile strength reaching as high as 2 GPa while keeping a decent tensile elongation above 10% and a reduction of area as high as 40%. Besides, through a careful control of strength contributions from multiple strengthening mechanisms, the nanostructured steels with superior strengths and low-temperature impact toughness can be obtained by avoiding the temper embrittlement regime. With appropriate Mn additions, these nanostructured steels can achieve a triple enhancement in ductility(total tensile elongation, TE of ~30%) at no expense of strengths(yield strength, YS of ~1100 to 1300 MPa, ultimate tensile strength, UTS of ~1300 to 1400 MPa). More importantly, these steels demonstrate good fabricability and weldability. In this paper, the microstructure-property relationships of these advanced nanostructured steels are comprehensively reviewed. In addition, the current limitations and future development of these nanostructured steels are carefully discussed and outlined.

Time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water

The laser induced breakdown spectroscopy(LIBS) is an element analysis technique with the advantages of real time detection,simultaneous multi-element identification,and in-situ and stand-off capacities.To evaluate its potential of ocean applications,in this paper,the time resolved laser-induced breakdown spectroscopy for calcium concentration detection in water is investigated.With the optimum experimental parameters,the plasma emission lifetime is determined to be about 500 ns with 532 nm laser excitation,and 1000 ns with 1064 nm laser excitation.The lowest detection concentration of 50 ppm is achieved for calcium detection in CaCl2 water solution using the 532 nm LIBS.Even better detection sensitivity is achieved using the 1064 nm LIBS,and the resulted lowest detection concentration of calcium is 25 ppm.The results suggest that it is feasible to develop LIBS as an on-line sensor for metal element monitoring in the sea.

The reason of Hopf’s and Oleinik’s proofs for countability of shocks being wrong

For the number of complete shock curves of a conservation law with one space variable,Hopf in 1950 for the Burger equation,and Oleinik in 1956 for the general,stated that it is at most countable.In 1979,the present author published an example to show that the statement of Hopf and Oleinik is wrong.But after so long time,the wrong statement for countability still appeared in some publications,which is at least partly due to that some ones felt difficult to understand Hopf and Oleinik’s proofs being wrong.So,pointing out where they went wrong becomes very necessary.