In the new century, people will extensively concern themselves with environment protection and natural resource saving. Their life style will be changed rapidly. Information system will become the most important part of our society. All of these will put forward the following challenging requirements to the electric power system for high economic characteristics, high reliability, high quality, high quantity and high density of power supply. As the conventional technology used in current power system is difficult to meet these requirements, breakthroughs of revolution in electrical technology is in urgent need. Superconducting technology is one of those breakthroughs. It is commonly recognized that superconducting technology will be widely used in the electric power system in the 21st century. This paper systematically analyzes the problems facing the electrical power industry in the 21st century and the potential of using superconducting technology in the future power system. The current states of applying superconducting technology to the electric power system are also overviewed.
China´s refining industry now has had fair strength after 50 years´ development. By the end of 1999, the annual capacity of crude oil processing had reached 250 million tons, which was ranked 4th in the world. At the turn of the century, China´s refining industry should solve a set of problems first, such as utilizing domestic and foreign crude oil resources as a whole, especially some problems in processing, storage, transportation and resource security of foreign crude oil. At the same time, in order to take up the challenges born of China´s entering WTO, it is necessary to enhance the overall competitive power against imported oil products in the respects of reducing the purchase cost of crude oil, raising facility utilization, cutting down the consumption of energy and material, prolonging production cycle, lowering production cost, improving the quality of products and meeting the requirements of environment protection.
The digital earth model is composed of three parts： digital frame model, digital elevation model, and digital earth-unit model. The question of building virtual earth in science mainly includes two sections： building the digital earth model and applying and developing modeling information effectively. The five characteristics of virtual earth and the key technologies for building digital earth model are introduced. This paper also discusses the seven engineering fields in which the digital terrain model is widely used. In the process of constructing ,researching, and developing the digital earth model, attention should be paid to environment pollution, plough land decrease, waterlogging and east-west regional variances, which have influence on China´s na-tional economic construction.
Innovation is the core competence and development source of a future-oriented company. The definition, characters and types of innovation are presented at first. There are four types of innovation： product innovation, process innovation, management innovation and market innovation. The innovation capacity of an enterprise does not depend upon the creation of innovators and methodology of innovation only, but, more importantly, is determined by the culture, management and reward systems of innovation in the company. For an enterprise to position itself competitively in the quick changing market environment, it is essential that everyone in the company be involved in modern innovation strategies and practices. Changes initiated to make people more motivated at work also serve to increase the level of innovation. People are the most critical elements in the innovation process and could be trained for creation. The implementation of innovation includes four main phases： the generation and activation of creative idea, preparation to realize it, realization of creative idea and transfering innovation into practice. The success and fail factors of innovation are discussed. At last the innovation management as a new business is introduced.
The speed of international social-economic development closely depends upon the growth of world energy consumption, which in turn has to meet the stringent environmental protection policy that controls the total amount of greenhouse gas released to the atmosphere in the burning of fuel. In order to achieve the sustainable development of all nations, it is advisable to give an outlook to the future situation of world oil and gas industry as the representatives of the non-regenerable energy resources. This paper presents an opinion on the future development of oil and gas industry based on limited data published in literature together with controversial forecasts by different authors and covers four subjects： (1) the demand and supply of oil and gas in the new century; (2) the specifications of oil products to meet the environmental regulations; (3) the role of unconventional oil in the energy industry and (4) the brilliant future of natural gas.
The writers propose to divert seawater from Guanli Harbor on the coast of Laizhou Bay with transversal canals and have it discharged into the Lower Yellow River at Lijin, about 110 km upstream of the river mouth (route B, Fig. 1). The flow diverted ranges from 500 to 1 500 m3/s, to be stipulated later in the feasibility study. This flow of “clear” seawater would strongly scour the channel downstream of Lijin and reduce its surface slope so much that for a flood of 3 000 m3/s an abrupt drop of 3.3 to 7.9m in the water surface would occur at Lijin. This drop would bring about retrogressive erosion of the riverbed upstream of the point of injection of seawater. The extent of this erosion is estimated to be 270 km upstream from Lijin. Thus a total of about 380 km of river channel would be scoured down. The reach downstream of Lij in would be transformed from an above - the - ground river to a down - in - the - ground river and the reach above Lijin would possess a deeper main channel. Safety in the defense against flood would thus be much enhanced.
For rational use of the Yellow River water resources, the State Council has allocated definite water right to every riparian province. A runoff of about 20 km3 is, however, to be reserved for sediment transport, in order to prevent the channel bed from excessive silting. With the facility available for the injection of seawater at Lijin, however, in the region down stream of Lijin one may redeem a portion of fresh water so reserved and restored the channel afterwards by scouring with seawater. Depending on capacities of pumping and reservoir storage available, the amount of fresh water redeemed may well run up to 1 km3 annually. This would be very valuable to the development of the estuarine region.
Since 1972, the Lower Yellow River has experienced a dry spell and has dried up from time to time. This has upset the ecological balance of the Bohai Sea because of interruption in the discharge of nutrient - carrying turbid water from the river. Scouring the estuary by diverting seawater will maintain a year round discharge of turbid water to the sea and help improve the ecological conditions as well as checking the receding of the coastline.
Turbid seawater being of greater specific weight than the clear seawater would form density current when discharged to the Bohai Sea. Sediment would then be conveyed to points far from the river mouth, thus delaying or even stopping the extension of the Yellow River delta. Moreover, when the river dries up, the river mouth would most likely recede under the scour of the discharging seawater because of lack of sediment supply from the drainage basin. Taking all the factors into account, one may expect little delta extension when seawater is diverted for scouring. Lijin, where seawater is injected, may then be taken as the effective location of the river mouth where the longitudinal equilibrium profile of the Lower Yellow River would terminate. This equilibrium profile would be lower than the original one by 4～12 m, depending on the estimated values of equilibrium slope for the final reach of the estuary. The hazard of levee breaching is thus much reduced.
The damage failure features and basic destruction mode of warplane under servicing in corrosion medium were studied. The method of establishing environmental spectrum for airport and the calculating methods of corrosion fatigue life under corrosion environments were described, based on the statistical analysis of corrosion failure types of major materials of aircraft structure. Some views for the research and development on corrosion fatigue of warplane in the future were put forward.
A new type of LD pumped Nd： YV04- KTP Q-switched green laser is demonstrated. By using the KTP crystal as both an electro-optic Q-switcher and a frequency-doubling crystal in type II phase matching for generating pulsed green beams, low loss and high efficiency characteristics were realized. Special temperature control technique and aspherical lens with smaller focus length were used in the laser, and all elements were fixed into a whole with epoxy. These measures improved the laser efficiency, output power and laser beam direction stability. Green power with up to 762 W peak output and 12 ns pulse width was obtained.
To meet the urgent needs of updating 1：10 000 scale and 1 ：50 000 scale topographic map for the whole territory of China, an integrated techinique for key elements revision is proposed, in which the topographic map is updated in raster mode through overlaying the precisely geo-rectified aerial or satellite image on the digitized map. The following issues are specially presented： 1) The scanning resolution of topographic map digitization in raster mode, which is not the same as the one in vector mode. 2) The concept of image array and graphic control point, instead of traditional pinpoint control point. 3) A local registration and adjustment method for rectifying aerial and space image using DRG without DEM. 4) Quantitative image interpretation by the guide of qualitative analysis. 5) The semi-automatic metrod for extraction of structural information from remote sensing image. Finally, a software developed on the basis of the proposed technique and its function are described, at the same time, an experiment result of 600 scenes of 1-50 000 scale topographic maps revision using the developed softwarte is presented.
The features and difficulties of the craft design as well as the experimental investigation of DACWIG (Dynamic Air Cushion Wing-in-ground Effect Craft) are described in this paper. Both model and full scale craft tests demonstrated that the static hovering characteristics, powering performance, seakeeping quality and aerodynamics balance as well as transverse and longitudinal stability of the craft were satisfied, due to taking a series measures in the craft design. So DACWIG has prospective future in both civilian and military use.
The multifunction oil for weapons is a unique product with excellent performances used in military forces of ground, navy and air under various climate conditions. As for its multiple performances the product needs excellent base oil with more kinds of additives. Among them there may be some synergistic or negative interactions that need to be well balanced. During the study various effects were investigated. Finally all the main problems were settled down and the lube oil for weapons with excellent performances in cleaning, lubricating and protecting was obtained.
In this paper a practical CAD/CAPP/CAM integrated system is introduced. This system has been developed by mechanical designers, process planners and NC progragmmers on the basis of a commercial CAD/CAM software named Pro/ENGINEER. It consists of three subsystems： Feature Recognition Subsystem, CAPP Subsystem and Automatical CAM Subsystem. In Feature Recognition Subsystem, machining features information of a part is obtained from a three dimensional part. In CAPP Subsystem, machining features information is analyzed, sets and sequences of the process planning are created automatically, tool and cutting parameters for each sequence are selected from tools library, the order of sequences is arranged. In Automatical CAM Subsystem, NC sequences for machining the part are created automatically according to the CAPP result. After the NC sequences in the machining process being simulated, the file of cutter location data is generated. Finally through a post processor, the NC code file is output and transmitted to a NC machine to machine the part.
This paper describes new general multi-mode non-destructive testing (NDT) of composite materials and bonded structures for detecting discontinuities (defects) , the only multi-mode one of its kinds. This technique which is based on sonic and ultrasonic testing performs five different modes of testing to detect disbond, unbond, delamination, porosity, crushed core and other defects in composite materials and bonded structures. It equally suits for applications in manufacturing, maintenance and repair of composite materials and structures which almost include them in common use now availability. Good repeatability and reliability have been found. This paper discusses the principles of the five sonic mode constitute multi-mode sonic general bondtester and demostrates the vast range of propect for general NDT from our and our internal and external comrades* much practical experinence.
The phase-shift PWM soft-switch technique for developing novel arc welding inverter is introduced in this paper, and a concrete circuit topology and its experiment results are given. The dynamic simulation and fuzzy logic control for arc welding inverter are analyzed. It is a new way for novel arc welding inverter development.
Many cities in China are now experiencing the booming period of metro construction. A critical and urgent problem is how to work out a sound network planning for the metro system before the concrete line implementation. Based on the experiences of metro network planning in China these years, the paper intends to explore some critical issues in this field. That includes the reasoning of the rational scale of the metro system, the spacial form and framework planning and the integration of the metro system with other public transport systems in the city.
N-4- (carboxyphenyl) retinamide (RE) is a new drug developed by the Institute of Materia Medica, Chinese Academy of Medical Sciences. The cancer chemopreventive action of R Ⅱ is reviewed in this paper. The multicenter clinical trials indicated that R Ⅱ was effective against premalignancies such as oral leukoplakia, vulvar leukoplakia, dysplasia of the uterine cervix and stomach. Preclinical studies demonstrated that R Ⅱ was a potent anti-mutagenic and anti-promotion agent. It has significant protective effects on chromosome aberration, and can inhibit ornithine decarboxyase (ODC) activity induced by 12-0-tetradecanoylphorbol-3-ac-etate (TPA) and decreases protein kinase C (PKC) activity. In a panel of experimental models including DM-BA induced buccal pouch carcinogenesis in hamster, DMBA and croton oil-induced skin papilloma, ni-trososamine induced forestomach carcinogenesis in mice, and N-butyl-N- ( 4-hydroxybutyl) -nitrosamine (BBN) induced bladder carcinogenesis in rats, it was demonstrated that R Ⅱ was a potent anti-carcinogenic a-gent. Electron microscopic studies and cell cycle kinetic analysis revealed that R Ⅱ could decrease malignant degree of tumor cells in terms of cell morphology and growth characteristics, and tumor cells differentiation. Action mechanisms studies indicated that R Ⅱ inhibited the expression of oncogene c-myc and enhanced the expression of c-fos.
In summary, R Ⅱ is a promising chemopreventive agent in terms of its anticarcinogenesis activity and clinical efficacy for the treatment of oral leukoplakia and vulvar leukoplakia.
The Problems caused by tailings disposal in metal mines are becoming more serious day by day. The total amount of tailings deposited by the Chinese metal mines is more than 4.0 billion tones, and the number is still increasing by 0.21 billion tones per year. The main features of metal mine tailings are extremely fine of particles, huge guantities, strongly poisonous and low bulky density for transportation. Tailings dam occupies large area of land. Accidents may be caused by tailings dam failure. Environmental pollution and underground water pollution are caused by tailings. It is necessary to carry out studies utilizing or treating tailings with new technologies. The comprehensive utilization of tailings should include recovering metal and non-metal elements from tailings, utilizing tailings to make building materials or magnetized fertilizer, etc. The treatment of tailings should include depositing tailings underground, utilizing tailings dam as a waste dump, and land reclaiming while depositing tailings paste. The final purpose of utilizing and treating tailings is to set up a “mine without tailings”.