Analysis of blast wave propagation inside tunnel

The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure.     

Mechanical model of domestic gas explosion load

With the increase of domestic gas consumption in cities and towns in China,gas explo-sion accidents happened rather frequently,and many structures were damaged greatly.Rational physical design could protect structures from being destroyed,but the character of explosion load must be learned firstly by establishing a correct mechanical model to simulate vented gas explo-sions.The explosion process has been studied for many years towards the safety of chemical in-dustry equipments.The key problem of these studies was the equations usually involved some ad-justable parameters that must be evaluated by experimental data,and the procedure of calculation was extremely complicated,so the reliability of these studies was seriously limited.Based on these studies,a simple mathematical model was established in this paper by using energy conservation,mass conservation,gas state equation,adiabatic compression equation and gas venting equation.Explosion load must be estimated by considering the room layout; the rate of pressure rise was then corrected by using a turbulence factor,so the pressure-time curve could be obtained.By using this method,complicated calculation was avoided,while experimental and calculated results fitted fairly well.Some pressure-time curves in a typical rectangular room were calculated to inves-tigate the influences of different ignition locations,gas thickness,concentration,room size and venting area on the explosion pressure.The results indicated that: it was the most dangerous con-dition when being ignited in the geometry centre of the room; the greater the burning velocity,the worse the venting effect; the larger the venting pressure,the higher the peak pressure; the larger the venting area,the lower the peak pressure.     

Application of automated image analysis to the identification and extraction of recyclable plastic bottles

An experimental machine vision apparatus was used to identify and extract recyclable plastic bottles out of a conveyor belt. Color images were taken with a commercially available Webcam, and the recognition was performed by our homemade software, based on the shape and dimensions of object images. The software was able to manage multiple bottles in a single image and was additionally extended to cases involving touching bottles. The identification was fulfilled by comparing the set of measured features with an existing database and meanwhile integrating various recognition techniques such as minimum distance in the feature space, self-organized maps, and neural networks. The recognition system was tested on a set of 50 different bottles and provided so far an accuracy of about 97% on bottle identification. The extraction of the bottles was performed by means of a pneumatic arm, which was activated according to the plastic type; polyethylene-terephthalate （PET） bottles were left on the conveyor belt, while non-PET bottles were extracted. The software was designed to provide the best compromise between reliability and speed for real-time applications in view of the commercialization of the system at existing recycling plants.     

完形填空练与析(英文)

A A Strange Greeting, a True Feeling Last week I was invited to a doctor's meeting at the Ruth hospital for incurables. In one of the wards a patient, an old man, got up shakily from his bed and moved towards me. I could see that he hadn't long to 1, but he came up to me and placed his right foot close to mine on the floor. "Frank! " I cried in astonishment. He couldn't 2, as I knew, but all the time 3 his foot against mine. My 4 raced back more than thirty years to the 5 days of 1941, when I was a student in London. The 6 was an air-raid shelter, in which I and about hundred other people slept every night. Two     

On the Advantages and Defects of the American Structuralism

During the years at the end of the nineteenth century and beginning of the twentieth century when Saussure was working out his ideas in Europe, synchronic linguistics was emerging independently, and in a very different style, in America, under the leadership of the anthropologist Franz Boas. Boas set a direction for American linguistics. The school founded by Boas was called structural linguistics. Beside Boas, the other two major representatives of this school during this period were: Sapir and Bloomfield.     

The ABC of ELT... TBL ——In this Issue,Jane and Dave Willis look at Task-Based Learning

TBL, also known as TBLT (task-based learning and teaching) and, in the USA, as TBL (task-based instruction) is an approach which uses communication tasks as the central focus for language teaching and learning. Basically the term task in TBL, refers to a meaning -focused activity. There are a number of definitions in the literature, but they can be characterized also follows: the learner s principle focus is on exchanging and understanding meanings, rather than on practice of pre-specified forms or patterns there is some kind of communicative purpose or goal set for the task, so learners know what they are expected to achieve by the end tasks can involve any or all four skills, e. g. a     

基因区分人与猿(英文)

Humans took a genetic leap away from the apes more than 2 million years ago, an international team of researchers announced in theProceedings of the NationalAcademy of Sciences.Using ancient fossils and advanced molecular techniques, the researchers determined that the gene mutation (变化,转变), when a gene fell out of the human genetic code (遗传密码), probably occurred 2. 5 to 3 million years ago. It was after humans stood upright (直立) - about 6 to 7 million years ago - but before hominid(原始人类) brains     

蠕变条件下完整岩石的起裂和扩展准则

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered.     

Children’s participatory design for sustainable development and community planning

The urban developments have been carried out by only professionals for a long time because of efficiency and safety. However, most residents are ordinary people. Therefore, it is necessary to change the awareness of sustainable living environments, not only on the construction side but also the residents. In recent years, the number of cases of residents’ participation in planning, maintaining, and repairing increased. However, sometimes youths and children, who might spend a lifetime longer than adults in a city after the developments have been done, are not included in this “Residents”. Concerning youth and children’s participation, CFC (child friendly city) is one of the good practices for sustainable development. It was launched by UNICEF (United Nations International Children’s Emergency Fund) and UN-Habitat in the Habitat II in 1996. City governments, especially in European countries, started to view CFC as their key concept for preservation and/or sustainable development. CFC means not only being “Children” friendly but also “All people” friendly. Various effects have been reported since the Historic Cities/districts included CFC in their city planning as a common concept, especially in education, community re-development, and operation and maintenance by the community. It is expected that better city planning in preservation and sustainable development can be achieved by adding CFC concept. In this research, an ideal way of city planning involving resident participation and the possibility in the future are analyzed based on case studies. Then a strategy of sustainable development and community planning involving youth and children’s participation is proposed.     

The Role of God in the Eyes of Early Puritans

In Christianity,God is always a significant role no matter in the physical or mental world.As for early Puritans,who proclaimed to purify God’s doctrine and lead an economical life,had an even stronger belief in God.When they began to set a colony in New England,they faced extremely tough challenges both from the native Indians and natural environment.During such a procedure,their reliance on God was clearly witnessed.Mary Rowlandson is an early colonist of New England,who was captured by native Indians and was finally redeemed.Basing on a close discussion of the narrative of her captivity and restoration,the paper would explore the importance of God in the eyes of early Puritans.     

Migration of Cr_2O_7~(2-) and Butanone in Soil and Groundwater System After the Tianjin Port 8·12 Explosion

After the Tianjin Port 8·12 explosion, an enormous amount of potassium dichromate(K_2Cr_2O_7) and butanone(CH_3COCH_2CH_3) leaked into the coastal soil–groundwater system, which potentially threatened the environment and human health. Determining the transport process of hazards is necessary to establish guidelines for remediating the contaminated area. This work aims to investigate the migration of potassium dichromate and butanone in the coastal soil-groundwater system through a coupling unsaturated–saturated numerical model, incorporating the HYDRUS model into the MODFLOW/MT3D model. In the unsaturated zone, two-dimensional HYDRUS model was applied, and its recharge flux at the bottom boundary was utilized as the input of MODFLOW/MT3D model in the saturated zone. Results showed that Cr_2O_7~(2-) migrated much faster than butanone in the unsaturated zone and reached the water table in about 1 year. In comparison, butanone was unlikely to enter the aquifer even 5 years later with a migration depth of about 2.2 m. Driven by groundwater, the Cr_2O_7~(2-) that entered the aquifer migrated about 161 m toward southeast 5 years later. In the saturated zone, the contamination plume covered mainly the southeast area due to the groundwater flow direction.     

Hybrid discrete particle swarm optimization algorithm for capacitated vehicle routing problem

INTRODUCTION The vehicle routing problem (VRP), which was first introduced by Dantzig and Ramser (1959), is a well-known combinatorial optimization problem in the field of service operations management and logis- tics. The capacitated vehicle routing problem (CVRP) is an NP-hard problem for simultaneously determining the routes for several vehicles from a central depot to a set of customers, and then return to the depot without exceeding the capacity constraints of each vehicle. In pr…     

Effect of a biological activated carbon filter on particle counts

Due to the importance of biological safety in drinking water quality and the disadvantages which exist in traditional methods of detecting typical microorganisms such as Cryptosporidium and Giardia, it is necessary to develop an alternative. Particle counts is a qualitative measurement of the amount of dissolved solids in water. The removal rate of particle counts was previously used as an indicator of the effectiveness of a biological activated carbon （BAC） filter in removing Cryptosporidium and Giardia. The particle counts in a BAC filter effluent over one operational period and the effects of BAC filter construction and operational parameters were investigated with a 10 m^3/h pilot plant. The results indicated that the maximum particle count in backwash remnant water was as high as 1296 count/ml and it needed about 1.5 h to reduce from the maximum to less than 50 count/ml. During the standard filtration period, particle counts stay constant at less than 50 count/ml for 5 d except when influenced by sand filter backwash remnant water. The removal rates of particle counts in the BAC filter are related to characteristics of the carbon. For example, a columned carbon and a sand bed removed 33.3% and 8.5% of particles, respectively, while the particle counts in effluent from a cracked BAC filter was higher than that of the influent. There is no significant difference among particle removal rates with different filtration rates. High post-ozone dosage （〉2 mg/L） plays an important role in particle count removal; when the dosage was 3 mg/L, the removal rates by carbon layers and sand beds decreased by 17.5% and increased by 9.5%, respectively, compared with a 2 mg/L dosage.     

古希腊的“泰坦尼克号”沉船

Greek and international team of divers and archaeologists has retrieved1stunning new finds from an ancient Greek ship that sank more than 2,000 years ago off the remote island of Antikythera(安提凯希拉).The Antikythera wreck was first discovered in 1900by sponge divers who were blown off course by a storm.     

Journal Critique:The Effect of Support Staff on Pupil Engagement and Individual Attention

In the past few years there has been a huge growth in the range and number of support staff in schools.A major context for policy and resourcing involving support staff in schools was the introduction in January 2003 by the Government,local Government employers and the majority of school workforce unions of the National Agreement(NA):" Raising Standards and Tackling Workload" .It set out a number of measures designed to continue to raise pupil standards,tackle teacher workload,including a concerted attack on unnecessary paperwork and bureaucracy,and review support staff roles(Blatchford,2006).     

Improved myocardial perfusion and cardiac function by controlled-release basic fibroblast growth factor using fibrin glue in a canine infarct model

Objective: Angiogenic therapy is emerging as a potential strategy for the treatment of ischemic heart disease but is limited by a relatively short half-life of growth factors.Fibrin glue (FG) provides a reservoir for controlledrelease of growth factors.The aim of this study was to evaluate the effects of basic fibroblast growth factor (bFGF) incorporating FG on angiogenesis and cardiac performance in a canine infarct model.Methods: Acute myocardial infarction was induced by ligation of the left anterior descending coronary artery (LAD).Group I (n=6) underwent ligation of LAD alone.In Group II,transmural channels were created in the infarct area (n=6).In Group III,nontransmural channels were created to locate FG cylinders containing bFGF (n=6).Eight weeks after operation,myocardial perfusion was assessed by single photon emission computed tomography,cardiac function by echocardiography,and vascular development by immunohistochemical staining.Results: Total vascular density and the number of large vessels (internal diameter ≥50 μm) were dramatically higher in Group III than in Groups I and II at eight weeks.Only the controlled-release group exhibited an improvement in regional myocardial perfusion associated with lower defect score.Animals in Group III presented improved cardiac regional systolic and diastolic functions as well as global systolic function in comparison with the other two groups.Conclusions: Enhanced and sustained angiogenic response can be achieved by controlled-release bFGF incorporating FG within transmyocardial laser channels,thus enabling improvement in myocardial perfusion and cardiac function.     

求有约束总极值的水平值估计方法

The penalty method is a popular method for solving constrained optimization problems,which can change the constrained optimization to the unconstrained optimization.With the integral-level set method,a new approach was proposed,which i sbriefer than the penalty method,to achivev the unconstrained optimization and a nonlinear equality.By studying the properties of the function.a level-value estimate algorithm and an implementation algorithm were given by means of the uniform distribution of the good point set.     

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A flu-id-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, struc-tural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic defor-mation subjected to intensive blast waves, and columns lost carrying capacity, subsequently lead-ing to the collapse of the whole structure. The approach coupling influence between struc-tural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.     

Australians win Nobel medicine prize

Two Australians won the Nobel prize for medicine on October 3, 2005 for showing that a bacterium rather than stress causes stomach inflammation and ulcers, after one of them drank a witches' brew of bacteria to prove the point. Experts said the discovery of the Helicobacter pylori bacterium by Barry Marshall and Robin Warren in 1982 was met with skepticism by the medical community,which did not think bacteria could survive in the acid conditions of the stomach. Marshall resorted to drinking a culture of the bacteria to give himself an ulcer and then to treat himself.     

The Attack on September 11th（高二适用）

New York. When the first jet struck 1 World Trade Center at 8: 48 a.m. on Tuesday, the people in 2 World Trade Center with a view of the instant dam-age across the divide had the clearest sense of what they,too,must do:get out fast.Katherine Ilachinski, who had been knocked off her chair by the blast of heat exploding from the neighboring tower, was one of those people. Despite her 70 years of age, Ms Ilachinski, an architect working on the 91st floor of 2 World Trade Center, the south tower,went for the stairs. Twelvefloors above her, Judy Wein,an executive,screamed and set off too.