“How were the earliest gears invented? Where were the sources and uses of the earliest gears? It is the mystery for men to unravel in a century.
This mystery seems soluble by unearthed gears or by “un-seaed” gears which were discovered from China, India. Greece, Rome and Egypt in 2 000 years ago.
But these gears made of bronze or cast-iron are mere 2nd-generation gears. The lst-generation gears madeof wooden. The invention of 1st generation gears would be accompanied with water machine water mill forgrinding grain. In ancient-civilization countries people lived together along rivers or sea-side 4 000 years ago. They came into contact with water. The “South-Pointing Chariot” is a unique Chinese invention before 200 B. C. It is the 1st set of differential mechanism in the world, the 1st self-control machine and the 1st robot machine in the world. It is the essence of 2nd-generation gears. The 3rd-generation gear is made of steel. This modern gears began at industry-revolutiion in 1800. The characteristics are using cutter with straight-edge to generat involute profile gears by mass production.
The 4th-generation gear will be coexisting with knowledge-economics. Creating the new high-strength composite materials and plastics to substitude for steel, of which the resources is getting shorten, will mark the beginning of the 4th-generation gears.
The trend of innovation of gears in the coming 50 years will be seeking miniaturization, puification and quietness, developing high-reliability, high-capacity, high-velocity and low-consumption of material, energy and weight.
The water resources in China are characterized by uneven regional and seasonal distribution. These features result in frequent droughts and floods, and unstable agricultural production. Per capita available water resources, ranking 108th worldwide, is very low although the country ´ s total is 2 810 km3. Regional distribution of water resources does not match that of land resources and an imbalance between water demand and supply has occurred seriously. With the growth of population, the industrial and urban water demand increased rapidly. The development of irrigation, affected by the lack of water resources, has basically been brought to a standstill. The sustainable social and economic development is facing greater challenges than any other country of the world. Moreover, owing to continuous deterioration of water environment and lack of construction funds, the water resources problems have become important constraints of social and economic development in China. This paper discusses the water problem and the countermeasures for sustainable development in 21st century.
In view of the present status and main problems in China´s cattle industry, it is necessary to increase the introduction of good breeds and the breeding sires. Embryo transfer is the best way for cattle improvement ,for it has the following advantages: simple operations, low cost, short period of improvement and less disease dispersal. The research status, the key technology and the necessity and possibility of industrialization of China* s embryo transfer are analyzed and described in this paper. Measures and methods for the application of embryo transfer technology to dairy and beef cattle are proposed.
Digital video is an important data format in multimedia information systems. Traditional video representation is just a time sequence——video stream, thus it is difficult for computer to recognize or perceive video in the content level. To efficiently access and utilize video information, a suitable organization of video data is critical. This paper proposes a video organization scheme, which arranges video into four layers： video program, episode, shot and image frame. This hierarchical structure provides a compact and meaningful video catalogue, which can be easily used for non-linear browsing and content-based retrieval of video data. To achieve such an organization, it needs not only detect the boundary of shots and episodes, but also extract the key frames of shots and select the representative shots and frames for episodes. This paper proposes a number of suitable criteria and techniques for video segmentation and organization, and integrates these techniques into a prototype system. Some organization results using real video data are presented, which show the effectiveness of this organization scheme.
Two ways to develop the aero-engines and their respective features are discussed in a summary manner. The regularity and importance of the mode of step by step development are discussed and justified with reference to the practices widely used at home and abroad for improving and developing aero-engines and to the experience therein, and a better organization and direction for improving and developing aero-engines are suggested to implement the planning of them.
It was predicted that the population of China will increase by 2〜3 hundred millions by the middle of next century, but the arable land will decrease by 18 million ha. This means that there will be a shortage of living space for 4〜5 hundred million populations, which will aggravate the situations of population, resources and environment. To expend living space is difficult duo to closing off afforested mountain for protection on upstream and recovering lakes from onec reclaimed farmland. However, the tidal flats along the coasts can provide a large amount of land resources. Historically, there were over 100 000 km2 obtained from land progression and reclamation. In recent 50 years, China has acquired 11 000～12 000 km2 new land with enhancing reclamation. This paper suggests making 10 000 — 15 000 km2 living space for 20～30 millions population to get employment before the year 2050. The reclaimation to lower tidal flats is the key and difficult point in the next 50 years. According to the sediment shortage from sea or river between artificial landmaking and natural landmaking, the artificial impelling siltation and bio-impelling siltation engineerings are necessary to make up for sediment shortage of natural land-making. Besides, it is also necessary to improve environmental monitor and prediction precision and to piake innovations on engineering technology and so on.
In this paper the critical area using imaging optics is discussed, i. e. the ground based astronomical telescopes, observing systems from the space to the Earth and the projecting lithographic systems. According to the trend of technical progress, it is unavoidable to use reflective optical systems, and consequently as-pherical surfaces. For optical system design, the main problem is how to construct an effective reflecting system which may be optimized by the optical CAD. The need of unobscurating entrance pupil leads using off-axis reflecting system and tilted mirror system. The key problem in fabrication is to make high accuracy, large relative aperture, high-order, large asphericity/aspherical slope and section symmetric surfaces. The null method is the principal way for testing aspheric surfaces up to now. The design of compensator for highorder, off-axis aspheric mirrors is worth studying yet.
The stiction and friction influencing the yield and reliability of MEMS are reviewed in this paper.The stiction, called release-related stiction, can occur within micron gaps of Si microstuctures during the etching of sacrifacial layer by HF and drying. It can also occur after packaging of the device due to over range of input signals and is called in-use stiction. It is concluded that the capillary force of water between two Si hydrophilic surfaces at separation gap of micron is the major contributor to the release-related stiction. The origin of in-use adhesion is from the chemical state of Si surface. Coating of anti-stiction films on the surface of Si microstructures and packaging of devices under dry atmosphere or vacuum are the most important methods to prevent the in MEMS devices from stiction. The preparation technology of anti-stiction films and its problems are described. Comparing with stiction, the friction is more complex. The commercially produced accelerometers and digital mirror devices are the devices with no direct contact friction. After using anti-stiction films, the stiction is fully prevented, and even the friction is apparently decreased. However, friction still exists in MEMS of direct contact moving parts. The wear resoluted from friction will decrease the reliability and lifetime of the devices. To fabricate the films with anti-stiction and wear-resitsting ability are the key research projects in high speed moving MEMS devices.
Recently millimeter wave imaging absorbs many attentions. Especially much research work has been done on the millimeter focal imaging because of its advantage of real time imaging. This paper analyzes extended hemispherical lens, which can be used in focal imaging. An integrated antenna array is placed at the back plane of the lens to receive the power focused by the lens. This structure can eliminate the effect of the surface wave exited in the thick dielectric substrates at millimeter wave wavelengths. Low loss and compact are its merit. Assuming an electromagnetic wave is incident on the lens surface, the field distribution in focal space of the lens is analyzed by using Stratton-Chu formula and ray tracing method. It will provide much information about the imaging performance of the lens. Experiments have been carried out for two types of incident waves, one is normally incident plane wave and another is Gaussian-beam. Good agreement has been found between experiments and calculation results. The lens antenna also can be used to eliminate the transition between paraboloidal antenna and integrated front-end in conventional integrated millimeter wave systems so that the system loss can be decreased and performance can be improved. Furthermore, the lens can be used to couple with a quasi-optical system. The results presented here will provide useful guidelines for the above mentioned applications.
The purpose of this thesis is to developing and exploiting an intelligent system for collision prevention, namely “Intelligent Collision Prevention Expert System for Navigation”(NICPES). The NICPES has a multi-unit and layering Knowledge Base systematic structure and a multi-unit Knowledge Representation (KR) which based on frame KR, production rule KR, procedure KR and neural network KR, to represent and store all kinds of knowledge for navigation collision prevention. The NICPES also builds a multi-inference system, which based on analogy inference, forward illation inference, conversion inference, neural network inference and meta-rule inference, to overcome the shortcoming of unitary inference. For-some problems in collision prevention region, the NICPES builds a set of models to solve them. These models comprise the models of judging collision risk, the model of determining collision prevention time and the model of classifying encounter situation. For multi-ship encounter situation, the NICPES puts forward a tactics to choose optimal collision prevention scheme based on Analytic Hierarchy Process (AHP) and builds a mathematical model that will be used to determine the optimal angle and sailing time during ship's turning for multi and single ship encounter situation. The simulation experiments show that the NICPES can analyze and judge various sailing cases and encounter situation ,and offer a reasonable scheme, which settle the collision problem effectively and ensure the sailing safety.
The trends of water quality change in the Yangtze River and the Yellow River in last 40 years were studied based on monitoring data collected from the Water Year Book of China (from the late 195 to the middle 1990´s) and the UN GEMS/Water program (1979〜1994). The results show that these two rivers each had their own trend of water quality change in respect of the major ions content. The water acidification trend mainly occured in the upper and middle reaches of the Yangtze River, which was caused by serious acid deposition due to the increasing S02 emission from coal combustion oxidation of the increasing nitrogenous fertilizer runs from farmland. The water quality concentration trend happened in the Yellow River, which was related to the decreasing of run off and the increasing of irrigation water. The total ion content of river water was increased by the concentration of irrigation water in farmland and its washing effect on soils.
The Inhibition of impurities of As, P, Si and Sn in the caustic decomposition of tungsten concentrates was studied. It indicated that in the presence of scheelite (CaWO4) and Ca(OH)2, during caustic decomposition of sdheelite with NaOH, impurities, such as As, P, Si, will be more completely inhibited in the cake in the forms of NaCaAsO4, Ca3(AsO4)2, Ca3(PO4)2，Ca5(PO4)3(OH)，CaSO3 and CaSnO3. It has been proved in laboratory experiment and industrial practice that the content of As and Si in the Na2WO4 solution from caustic decomposition of scheelite and wolframite mixed concentrates is only 20%〜30% of that from caus-tic decomposition of wolframite concentrates with the same contents of WO3 and impurities.
Measurement is an important means for obtaining information in research and production. Both the quality of products and the productivity of production highly depend on measurement. An important trend in the development of measurement is its merging with information technology. The requirements in high accuracy of measurement, on-line and dynamic measurements, measurements of complicated parameters and under complex conditions and intelligent measurements ask for the merging of measurements with information technology. This merging is carried out through the whole process. Modulation and demodulation, data sampling and reconstruction, signal merging, data compression, filtering, signal transformation, time series analysis, spectrum analysis, data fitting and modeling, pattern recognition, neural network, simulation and virtual measurement, error separation, error compensation, redundancy technique, decision making, intelligent techniques, etc. , are widely used in measurements. Some practical examples of this merging are given in the paper. The accuracy of coordinate measuring machines (CMMs) can be greatly enhanced by using error compensation technique. Modeling, error calibration and compensation software are three key techniques in error compensation of CMMs. Applications of redundancy technique in roundness and spindle error motion measurement, in large scale metrology are presented as well. Redundancy technique provides a powerful means in optimization of measurements, system self-calibration, error compensation, recovering the lost information and many other applications.
The design features and the evolution of the Amphibious wing in Ground Effect Craft (AWIG) (also so called Dynamic Air Cushion Wing-in-Ground Effect Craft, DACWIG) in China are described in this paper. The prospect of developing a novel type of WIG, with high speed, fine seaworthiness, marvelous amphibious, and being able to fly in/beyond ground effect zone and softly land on ground, as well as maneuver in air (just like the Russian novel type of WIG,Экранолë“тИВОЛГА-2”)，for both dvil and military application is full of hope.
The development and creation of measuring instrument transformers and their testing equipment in improving accuracy and performance since the end of fifties is described. They include the development in error compensation for instrument transformers, high accuracy instrument transformers with a current booster or voltage booster, current comparators and two-stage instrument transformers, the comparator-type calibrators and its testing instruments, digital calibrators, etc. Future work in this field, will involve the development of instrument transformers with small secondary current and voltage, application of computers and microprocessors in instrument transformers and their testing equipment, etc.
This paper describes the concept of new-type light-gage steel structure system and discusses the characteristics of it. Some current developments of this system are introduced. The problems that we faced and will face have been put forward. Some suggestions have also been made to develop new light-gage steel structure in China.
Oil-bearing materials are the main source of vegetable oils and proteins. Some fatty acids and certain structured lipids have particular biological functionality. Important progress has been made in this respect in recent years. Certain amount of socalled wastes are produced simultaneously along with the vegatable oils and proteins production, which have not been utilized perfectly for a long time. Actually, many value-added prod-ucts can be isolated from the “wastes”，such as lecithin, tocopherols, tocotrienols, plant sterols and stanols, isoflavones, saponins, phytic acids, trypsin, oligsaccharides, phenolic acids, etc. Then are considered to be functional components. Due to the particularity of the functional components, current technology and equipments of oil industry are not totally adaptable to the requirement of their isolation. Thus, the innovations of fats and oils technology as well as the utilization of biotechnology in making structured lipids are of great significance .
The era of information agriculture is commencing in the new century. Information agriculture will be the research frontier for the reasonable exploitation and utilization of agricultural resources, increase of crop yield, reduction of agricultural costs, mitigation of environment pollution and improvement of the international market competitive power of agricultural products. It is foreseen that biological engineering and agricultural information technology will be the two technical backbones for China's agriculture in the new century, and will be essential to realize China´s agricultural modernization. The agricultural information science, technology and engineering are brifly summarized in this paper. In the 21st century, China's agricultural information science, technology and engineering should closely follow the international frontier and implement span development ：not only develop and apply existent agricultural information technologies, those internationally hotspot topics should also be studied and tested in advance, to speed up the agricultural modernization in China through the development of agricultural information engineering.
With the development and wide application of information science in agriculture as a new branch from agricultural technology system, agricultural information engineering has been gradually developed. It is a promising applied technology and an important technologyical support for realizing China's agricultural modernization. The scientifically combining of agriculture and information science created the science of agricultural information. The embodiment and application of information technology in all of the agricultural fields have pushed the development of agricultural information technology. Agricultural information engineering results from the research and application of agricultural information science and agricultural information technology. The basic contents of agricultural information science include the mechanism of agricultural information, information feature, information classification and coding, information reproducing and information linkage, etc. Agricultural information technology is associated with the technology of agricultural information resource acquisition and management, technology of information system, technology of information precise positioning, technology of agricultural auxiliary decision-making, computer modeling, simulation and virtual technologies, artificial intelligence and expert system technologies, automation technology, multimedia and network technologies, etc. The technological system of agricultural information engineering consists of agricultural information resource acquisition system, information management system, agricultural exploitation decision-making system, synthesis modeling system of regional resource exploitation, agricultural expert system and the virtual environment system of agricultural science knowledge innovation, etc.