Engineering and Electrical Engineering?Supply and Demand

Change in employment of engineers is shown to be related to the Deutsch and Shea Index of Engineering Demand. A relationship is given that shows the changes in engineering employment on a quarterly and annual basis. Engineering employment has turned upward for the first time since the last quarter of 1969. We have displaced and stored over 90 000 qualified engineers since 1969, in addition to displacing over 40 000 not qualified by an engineering education. Estimates by some of the need for 48 000 engineers per year is shown to be highly questionable. Current demand is still insufficient to absorb the current output without displacing some currently employed. It is suggested that demand in specialties can be determined by advertising lineage devoted to specialties in the same manner that the engineering demand is determined by the Deutsch and Shea Index. The years 1970, 1971, and 1972 were characterized by a decrease in employment of 62 000 engineers, 150 000 new graduates, 25 000 immigrants, and only 55 000 normal retirements and deaths.     

Thermal and Chemical Evolution of Comet Nuclei and Kuiper Belt Objects

The structure and composition of comet nuclei are mainly altered during two short phases that are separated by a very long hibernation phase. Early evolution—during and immediately after formation—is the result of heating caused by radioactive decay, the most important source being ²⁶Al. Several studies are reviewed, dealing with evolution throughout this phase, calculated by means of 1-D numerical codes that solve the heat and mass balance equations on a fixed spherically symmetric grid. It is shown that, depending on parameters, the interior may reach temperatures above the melting point of water. The models thus suggest that comets are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in the cold subsurface layer. As the initially amorphous ice is shown to crystallize in the interior, some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. The second phase of evolution occurs when comet nuclei are deflected into the inner solar system and is dominated by the effect of solar radiation. Now the outer layers are those mostly affected, undergoing crystallization, loss of volatiles, and significant structural changes. If any part of a comet nucleus should retain its pristine structure and composition, it would be well below the surface and also well above the core.     

Thermal Evolution and Magnetic Field Generation in Terrestrial Planets and Satellites

Of the terrestrial planets, Earth and Mercury have self-sustained fields while Mars and Venus do not. Magnetic field data recorded at Ganymede have been interpreted as evidence of a self-generated magnetic field. The other icy Galilean satellites have magnetic fields induced in their subsurface oceans while Io and the Saturnian satellite Titan apparently are lacking magnetic fields of internal origin altogether. Parts of the lunar crust are remanently magnetized as are parts of the crust of Mars. While it is widely accepted that the magnetization of the Martian crust has been caused by an early magnetic field, for the Moon alternative explanations link the magnetization to plasma generated by large impacts. The necessary conditions for a dynamo in the terrestrial planets and satellites are the existence of an iron-rich core that is undergoing intense fluid motion. It is widely accepted that the fluid motion is caused by convection driven either by thermal buoyancy or by chemical buoyancy or by both. The chemical buoyancy is released upon the growth of an inner core. The latter requires a light alloying element in the core that is enriched in the outer core as the solid inner core grows. In most models, the light alloying element is assumed to be sulfur, but other elements such as, e.g., oxygen, silicon, and hydrogen are possible. The existence of cores in the terrestrial planets is either proven beyond reasonable doubt (Earth, Mars, and Mercury) or the case for a core is compelling as for Venus and the Moon. The Galilean satellites Io and Ganymede are likely to have cores judging from Galileo radio tracking data of the gravity fields of these satellites. The case is less clear cut for Europa. Callisto is widely taken as undifferentiated or only partially differentiated, thereby lacking an iron-rich core. Whether or not Titan has a core is not known at the present time. The terrestrial planets that do have magnetic fields either have a well-established inner core with known radius and density such as Earth or are widely agreed to have an inner core such as Mercury. The absence of an inner core in Venus, Mars, and the Moon (terrestrial bodies that lack fields) is not as well established although considered likely. The composition of the Martian core may be close to the Fe–FeS eutectic which would prevent an inner core to grow as long as the core has not cooled to temperatures around 1500 Kelvin. Venus may be on the verge of growing an inner core in which case a chemical dynamo may begin to operate in the geologically near future. The remanent magnetization of the Martian and the lunar crust is evidence for a dynamo in Mars’ and possibly the Moon’s early evolution and suggests that powerful thermally driven dynamos are possible. Both the thermally and the chemically driven dynamo require that the core is cooled at a sufficient rate by the mantle. For the thermally driven dynamo, the heat flow from the core into the mantle must by larger than the heat conducted along the core adiabat to allow a convecting core. This threshold is a few mW?m^?2 for small planets such as Mercury, Ganymede, and the Moon but can be as large as a few tens mW?m^?2 for Earth and Venus. The buoyancy for both dynamos must be sufficiently strong to overcome Ohmic dissipation. On Earth, plate tectonics and mantle convection cool the core efficiently. Stagnant lid convection on Mars and Venus are less efficient to cool the core but it is possible and has been suggested that Mars had plate tectonics in its early evolution and that Venus has experienced episodic resurfacing and mantle turnover. Both may have had profound implications for the evolution of the cores of these planets. It is even possible that inner cores started to grow in Mars and Venus but that the growth was frustrated as the mantles heated following the cessation of plate tectonics and resurfacing. The generation of Ganymede’s magnetic field is widely debated. Models range from magneto-hydrodynamic convection in which case the field will not be self-sustained to chemical and thermally-driven dynamos. The wide range of possible compositions for Ganymede’s core allows models with a completely liquid near eutectic Fe–FeS composition as well as models with Fe inner cores or cores in with iron snowfall.     

Study of aerodynamic and inertial forces of a experimental and numerical methods

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and experiment. To obtain the real deformation pattern of the flapping wing, the digital image correlation technology was used to measure the dynamic deformation of the wing. The dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic effects. The dynamic deformation data were further used to calculate the inertial forces...     

Competitive Environment and Reform Conceptions

There are various signs that indicate the pace of civil aviation reform is quickening withlittle buzz.People hold a common understanding that the air fare hearing, which was held in mid-Julyafter being postponed by SARS, is an important progress of market-oriented reform of civilaviation despite controversies among representatives and different remarks from the society.As a development strategy of Chinese civil aviation, regional aviation has been proposedfor many years. However, few actions…     

Preparation and Photoluminescence of ZnO Nanostructures

Porous anodic alumina (PAA) hosts with ZnO nanoparticles loaded in were prepared by immersing PAA films in an aqueous solu-tion of zinc acetate and then annealing at high temperatures. Highly ordered ZnO nanodot arrays were produced using the method in combination of PAA template with RF magnetron sputtering deposition. The photoluminescence of the ZnO/PAA composite and the highly ordered ZnO nanodot arrays were investigated by means of a fluorescent spectrometer. The ZnO/PAA composite exhibits intense and broad photoluminescence spectra with the peak position at around 485 nm. The ZnO nanodot arrays have a strong UV light emissive peak at about 380 nm and a wide light emissive peak at 460 nm-610 nm at the room temperature.     

Web-Enabled Remote Machine Monitoring and Prognostics

1 INTRODUCTION Today’s machine tool industries arefacing unprecedented challengesbrought about by development ofoutsourcing and low cost manufac-turing in Asia. Manufacturingoutsourcing provided many opportu-nities but also added challenges toproduce and deliver products with     

Growing Up Amid Wind and Rain

Beijing has entered into golden autumn, the most beautiful season of the year.The season also sees the golden period of this year for the air transport market, whichwas badly hit by SARS. According to the CAAC and the State Statistics Bureau, totaltraffic turnover, Passenger transport volume and cargo & mail transport volume of civil     

Products-the Basis forEnterprise Existence and Development

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Modeling and Control for Magnetostrictive Hysteresis

To deal with the rate-dependent hysteresis presented in a magnetostrictive actuator, a new method of modeling and control is pro-posed. The relationship between inputs and outputs of the actuator is approximately described by a dynamic differential equation with two rate-dependent coefficients, each expressed as a polynomial of frequency. For a given frequency, the coefficients will be able to be estimated by approximating the experimental data of the outputs of the magnetostrictive actuator. Based on this model, a quasi-PID con-troller is designed. In the space of the coefficients and frequency, the stable domain of closed loop system with hysteresis is analyzed. The numerical simulation and experiments have born witness to the feasibility of the proposed new method.     

Potentials of manufacture and repair of nickel base turbine components used in aero engines and power plants by laser metal deposition and laser drilling

IntroductionExpensive turbine parts like HPT(HighPressure Turine)blades or vanes are replaced bynew parts in case of damage.For example theburn through of the inner side of a blade or vane(Figure 1)is a frequently appearing damage,which cannot be repaired…     

Manufacturing With Lasers Developments and Opportunities

Developments and opportunities for manufacturing with lasers are considered in three broad themes. Process enhancements, in particular hybrid-laser arc welding and twin spot laser welding are described. Two examples of novel manufacturing processes (laser joining of aluminium to steel and laser direct metal deposition) are considered. Finally, a new laser source (Yb: YAG fibre laser) is introduced as an additional competing processing capability.     

Cooling and lubrication techniques in grinding:A state-of-the-art review,applications, and sustainability assessment

Grinding technology is an essential manufacturing operation, in particular, when a component with a superfinishing and an ultra-resolution is yearned. Meeting the required strict quality checklist with maintaining a high level of productivity and sustainability is a substantive issue. The recent paper outlines the lubrication and cooling technologies and mediums that are used for grinding. Furthermore, it provides a basis for a critical assessment of the different lubrication/cooling techniques ...     

Mixing and combustion characteristics in a scramjet combustor with different distances between cavity and backward-facing step

The mixing and combustion characteristics in a cavity flameholding combustor under inlet Mach number 2.92 are numerically investigated with ethylene injection. Dimensionless distance is defined as the ratio of the actual distance to the height of the combustor entrance. The cavity shear-layer mode, the lifted cavity shear-layer mode, and jet wake mode with upstream separation are observed respectively with dimensionless distance equals to 1.5, 4.5, and 7.5. In both non-reacting and reacting flow...     

Characterization and Microstructure of PLZT RAINBOW Ceramics

RAINBOW陶瓷是一种具有内部应力偏移，并具有特殊的拱形结构的大位移驱动材料，它是通过将普通的压电陶瓷在高温下化学还原制备所得。实验表明，PLZT压电陶瓷具有较好的还原性能，还原层厚度与时间有线性关系，理想的还原条件为：950℃保温1～1．5h；电镜照片显示RAINBOW陶瓷有明显的分层结构，还原层表现出穿晶断裂而未还原层则是沿晶断裂的特征。XRD谱发现还原层主要由金属Pb及PbO，ZrO2，ZrTiO4等氧化物组成，原先的晶体结构已不存在；还原机制的理论分析与实验结果一致。     

A composite disturbance observer and H_∞ control scheme for flexible spacecraft with measurement delay and input delay

In this paper, the attitude control algorithm of flexible spacecraft with unknown measurement delay and input delay based on disturbance observer is designed. The influence of measurement delay and input delay on the attitude control system and disturbance observer is analyzed. The disturbance estimation error equation is transformed into a differential system with a pure delay. Then, the observer gain is chosen based on the 3/2 stability theorem to ensure the stability and disturbance attenuation performance of the pure delay system. Next, the controller gain is designed based on the Linear Matrix Inequality(LMI) approach to guarantee the stability of the composite system and achieve H_∞ performance with two additive delays. The simulation results show that the proposed method can improve the anti-disturbance ability of the attitude control system.     

Electric Fields and Magnetic Fields in the Plasmasphere: A Perspective From CLUSTER and IMAGE

The electric field and magnetic field are basic quantities in the plasmasphere measured since the 1960s. In this review, we first recall conventional wisdom and remaining problems from ground-based whistler measurements. Then we show scientific results from Cluster and Image, which are specifically made possible by newly introduced features on these spacecraft, as follows. 1. In situ electric field measurements using artificial electron beams are successfully used to identify electric fields originating from various sources. 2. Global electric fields are derived from sequences of plasmaspheric images, revealing how the inner magnetospheric electric field responds to the southward interplanetary magnetic fields and storms/substorms. 3. Understanding of sub-auroral polarization stream (SAPS) or sub-auroral ion drifts (SAID) are advanced through analysis of a combination of magnetospheric and ionospheric measurements from Cluster, Image, and DMSP. 4. Data from multiple spacecraft have been used to estimate magnetic gradients for the first time.