Single-Wafer-Processed Self-Testable High-$g$ Accelerometers With Both Sensing and Actuating Elements Integrated on Trench-Sidewall

A single-wafer-processed high-$g$ piezoresistive accelerometer is reported. The microsensor has an in-plane self-caging cantilever configuration, in which an electrostatic self-testing function is integrated on-chip. Both the sensing piezoresistors and the self-test actuating electrodes are integrated on vertical sidewalls of the laterally deflecting cantilever. For single-wafer-based fabrication of the self-testable piezoresistive accelerometer, a trench-sidewall micromachining technology is developed, which is capable of integration of both boron-diffused piezoresistive sensors and electrostatic actuators on deep trench sidewalls. In addition, the technology can realize electrical continuity from the vertical trench-sidewall to the wafer surface. After design and fabrication of the accelerometers for a 200 000 g measure-range, characterization was performed to evaluate the developed trench-sidewall integration technology and to test the self-testable high-$g$ accelerometers. A linear I-V relationship for the sidewall-diffused piezoresistor is measured with satisfactory sidewall-to-surface electric-transfer properties. The electrical isolation between adjacent elements on the sidewall shows a breakthrough voltage of about 55 V. Moreover, with the single-chip integrated lateral-actuating structure, both static and dynamic self-testing functions are realized. The measurement of the accelerometer results in a sensitivity of about 1 $~mu$V/g/3.3 V, noise-limited vibration resolution of about 1 g and zero-point temperature drift of lower than 100 ppm/$^{circ}$ C.      

A Novel Two-Axis CMOS Accelerometer Based on Thermal Convection

Accelerometers based on thermal convection use a tiny bubble of heated air and pairs of temperature sensors hermetically sealed inside the sensor package cavity. In this paper, we successfully design and fabricate a novel thermal-bubble-based micromachined accelerometer with the advantages of minimized solid thermal conductance and higher sensitivity. The proposed accelerometer consists of a microheater and two pairs of thermopiles floating over an etched cavity and is constructed by our proposed microlink structure. Two-dimensional acceleration detection is easily realized using the microlink structure, and it can be applied to the technology of inclinometers, anemometers, and flowmeters. The heater and thermopiles are connected by netlike microlink structures, which enhance the structure and greatly reduce the solid heat flow from the heater to the hot junctions of the thermopiles. The samples are fabricated by the TSMC 0.35-$muhbox{m}$ 2P4M CMOS process, which has been provided by the National Chip Implementation Center (CIC). Our design has proved to be applicable for commercial batch production with outstanding strong structures and uniform quality. We measure the output signal by inclining the sensor to evaluate the performance of this accelerometer. The best sensitivity of 22 $muhbox{V}/ hbox{g}$ was obtained from acceleration versus output voltage under several experimental conditions.      

加速度计冲击特性的绝对校准方法

从描述测量系统的微分方程出发,用系统的输入输出数据辨识系统的离散传递函数,弥补在加速度计灵敏度校准中不能给出加速度计动态特性的缺陷,再应用系统的离散传递函数将加速度计输出信号恢复为一定的动态特性范围内“真实”的现场冲击加速度－时间历程。     

Seismic Velocity Sensor With an Internal Sky-Hook Damping Feedback Loop

This paper presents a new seismic velocity sensor with an internal feedback control loop. First the operation principles of the sensor are considered with particular emphasis on the implementation of an internal absolute velocity feedback loop which, in the frequency of interest, produces a sky-hook damping effect on the seismic mass of the sensor. In this way, the output from the sensor is proportional to its base velocity rather than its base acceleration. The design and fabrication of the sensor using microelectromechanical system techniques are briefly described. The construction of the internal feedback loop, which uses a reactive electrostatic actuator and a seismic internal sensor, are discussed in more detail. Finally the results of experimental tests are presented, which highlight that: a) in the frequency of interest, the output signal of the sensor is proportional to its base velocity; b) the fundamental resonance of the seismic sensor is attenuated by the active damping effect produced by the internal feedback control loop, and c) above this fundamental resonance, the response rolls off at a rate of 3 dB per decade and lags by 90$^{circ }$ instead of the 180$^{circ}$ phase lag of a standard seismic accelerometer sensor.      

Testing Transverse Sensitivity of Linear Single-Axis Pendulous Accelerometer with Double Turntable Centrifuge

Current ISO standard methods for testing transverse sensitivity of accelerometers are vibration-based. They have difficulties in producing low-frequency vibration for various reasons. This paper introduces a double turntable centrifuge (DTC) to test the accelerometer transverse sensitivity at low frequencies (from 0.01 to 10 Hz). The proposed method can avoid limitations of traditional vibration-based schemes for transverse sensitivity test. In this paper, a theoretical analysis of the method is followed by a presentation of the experimental set-up, and the measurement procedure of a linear single-axis pendulous accelerometer. According to the theoretical analysis and experimental results, it is practicable to test the low-frequency transverse sensitivity with a DTC. The method proposed here can test accelerometer transverse sensitivity at low-frequency with large amplitudes (up to 700 m/s²), and directly measure the angle of the transverse sensitivity with high resolution. It can be a supplement to the standard methods for testing accelerometer transverse sensitivity at low-frequency.     

On the nature of the fourth sound

The density-density correlation function of He II bounded by solid walls is calculated in the hydrodynamic region. The migration of its poles as a function of the resistance parameter is investigated, and it is found that the fourth-sound pole can only be related to the first-sound pole far enough (_s0/₀>1/9) from the critical temperature. Otherwise, it arises from a mixture of the first- and second-sound poles. The contributions of poles to the sum rules are also discussed.     

Shirokov's formula connecting the transfer properties of liquids with the velocity of sound

According to existing data for u, , , it is established that Shirokov's formula can become a quantitative relation if we introduce into it a dimensionless quantity , which depends on the temperature and pressure.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 2, pp. 332–335, February, 1981.     

Defining the concept of measurement

Conclusion The suggested more precise definition of measurement (in our opinion only apparent) has not been attained and in general it is doubtful whether a revision of the above definition is required with any degree of urgency. The new definition has no advantages as compared with the generally-accepted definition, quite apart from the fact that it is too cumbersome. The criticism of the generally-accepted definition of the concept measurement has not been sufficiently substantiated, and as yet there is no reason for rejecting it. However, the authors deserve the gratitude of metrologists for an interesting approach to the problem.Contribution to a discussion, see Izmeritel'naya tekhnika, 1961, No. 12.     

Generational similarities and differences in researchers&;#39; professional ethics: An empirical comparison

Summary Felsenstein's (1985) method of phylogenetic independent contrasts is probably the most commonly used technique in evolutionary biology to study adaptation of organisms to their environment, taking phylogeny into account. Here, we performed a scientometric evaluation of all 1462 articles that cited Felsenstein (1985) between 1985 and 2002, in order to analyze the impact of his comparative method on the evolutionary research program and what has been done since it. We found that Felsentein's (1985) article can be classified as a “hot paper' or a breakthrough contribution, since it was the most cited article from The American Naturalist published in 1985. Also, it can be considered as a “citation classic', since it is the third more cited paper in The American Naturalist from 1945 to 2002. In general, papers that cited Felsenstein (1985) were published in high-impact journals, and most of them are theoretical articles indicating that biologists are aware of statistical and conceptual problems in dealing with comparative methods.     

Modelling of Gas Streams Taking Account of Viscosity

It is shown that in some cases in studying the interaction of a technical device with a gas stream among similarity criteria it is possible to introduce a dimensionless value as the ratio of a new dimensional complex (the product of dynamic viscosity and kinematic viscosity having a dimension of force) into the reaction force of a mechanical device under a hydrogas-dynamic influence. Then the choice of model gases and their ranking is facilitated; it is also possible to vary the gas stream by changes in pressure and temperature making it possible to embrace the field of corrosive and toxic gas operation. The method may be extended to liquid streams.__________Translated from Izmeritelnaya Tekhnika, No. 2, pp. 46–48, February, 2005.     

Investigating the thermal stability of transistor circuits with a high input resistance

Conclusions On the basis of the above experimental investigations it is possible to state the following. Taking into account the small size of the automatic device for measuring the vibration parameters during the drilling of boreholes and its subjection to considerable temperature effects, it is advisable to use a thermally-stable circuit with a high input resistance of 10 M. The utilization of silicon transistors in this circuit provides completely adequate input resistance for working with piezoelectric vibration transducers up to a temperature of +100°C.In case it is necessary to raise still further the circuit input resistance, it is advisable to use silicon transistors with a higher current gain , which are in short supply (for instance, transistors P504, P504A, P505, and P505A).The use of transistors with a larger makes it possible to apply a deeper negative feedback, which raises the input impedance and improves the gain stability of the stage with respect to temperature effects. The above circuits can also be used in other measuring and electronic devices which are subjected to considerable ambient temperature effects.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 54–55, October, 1970.     

Life in a multidimensional world

The methodology of the science of science is claimed to be plagued by one-dimensional thinking, and it is urged that a multi-dimensional view be adopted instead. In a one-dimensional model cause is a meaningful word, superlatives can be used, dichotomous thinking is realistic, with a resultant zero-sum mentality, and the make a hypothesis-find a correlation method makes sense. In the multidimensional framework these four characteristics are unsuitable, and instead a quite different set of questions arise as appropriate. This is illustrated on five examples taken from among currently interesting questions in the science of science. Following some remarks about simplicity and about the role and limitations of multiple regression analyses, it is concluded that, among other things, more purely phenomenological studies are needed to make progress in the science of science.     

On the possible superfluidity of 6He—Its phase diagram and those of 6He-4He and 6He-3He mixtures

The properties of pure ⁶He and ⁶He-⁴He and ⁶He-³He mixtures are studied within the context of the quantum theorem of corresponding states. For pure ⁶He, it is found that there is a small, but definite, region where it is expected to be superfluid. For the ⁶He-⁴He mixture, it is found that there is a -eutectic temperature, approximately 1.2 K, below which it is expected that both ⁶He and ⁴He will be part of the superfluid at all concentrations. Experiments to observe ⁶He superfluidity are discussed, and it is concluded that such experiments are feasible, although they may be quite difficult to carry out. Experiments are discussed to use a ⁶He generator (should it be possible to construct it) as a probe to study various properties of liquid and solid helium.Work supported in part grant from the National Science Foundation.     

Uncertainty of a measured result and confidence error of measurements

An analysis is made of the known information concerning the concepts of error and uncertainty and it is concluded that they are identical.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 14–17, August, 1994.     

Effect of magnetic pickups on the input transformers of measuring devices

Summary The asymmetry coefficient for all types of transformers depends on the core permeability, which in turn depends on the ratio ofl _av/s or D_av/s. In order to reduce core permeability, it is necessary to select toroidal cores with a small diameter and a large cross section, and provide laminas of O-shaped and shell-type cores with a shape to make these cores short and large in cross section.Under actual operating conditions, transformers with toroidal cores provide a higher immunity from noise. For the same designs, sizes, and relative parameter dispersions, the transformers with toroidal and O-shaped cores have a ratio of _max equal to 1.6. In shell-type transformers it is imperative to take into account the polarity of their windings on which the transformer's noise stability depends to a great extent.     

On the stability of plane parallel convective flow

Summary The Lyapunov direct method is used to study the nonlinear stability of parallel convective shear flows of an incompressible fluid heated from below with stress-free boundaries. In particular it is showed that plane Couette and plane Poiseuille flows with linear temperature profile are conditionally asymptotically stable, in a stronger norm than the energy norm, whenever the Rayleigh number ² is less than 657.511, independent of the Reynolds numbersR.     

Use of classical stefan problem for initializing solution in the numerical prediction of freezing

The exact solution of the classical Stefan problem is examined from the point of view of using it as an initial solution in numerical solutions of appropriate problems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 5, pp. 847–850, November, 1982.     

Microstructural evolution in rapidly solidified Al-Cu-Si ternary alloys

Several Al-Cu-Si alloys were melt spun to produce stable, fine scale microstructures suitable for superplastic deformation and consolidation. Scanning electron microscopy of the ribbon cross-sections reveal two distinct alternating microstructural morphologies, suggesting transitions in solidification behavior. One structure consists of intimately interlocked -Al and (Al₂Cu) phases with dispersed spheroids of (Si). The other structure consists of equiaxed or cellular-dendritic -Al with interdendritic and (Si). The latter was found in the middle portion of the ribbon cross-section when cast at a low speed, and throughout the ribbon cross-section when cast at high speed. The dendritic structure appears to result from independent nucleation events in the undercooled liquid ahead of the solid-liquid interface. The solidification mechanism for the interlocked structure appears to involve multiple nucleation of the phase followed by its cooperative growth with the -Al phase. This cooperative growth is unlike that which forms a lamellar structure, as it results in a branched, randomly oriented network. We postulate that the (Si) phase is the first phase to form from the undercooled liquid, and it is uniformly dispersed throughout the undercooled melt. The (Si) spheroids provide nucleation sites for the phase because of its observed association with the phase. The -Al grain size varies from 1 m near the wheel side surface of the ribbon to 8 m with sub-grains near the free surface. The size of the and (Si) phases is on the order of a m and less. The microstructural size scale appears to be small enough for this material to exhibit superplastic behavior when deformed.     

Formulation of an Experiment for Detecting New Long-Range Forces

An experimental scheme is proposed for detecting new long-range forces by utilizing a spherical cavity excavated from a sphere and placing a fixed torsion balance within it. It is shown that for the optimal distance between the axes of rotation of the sphere, the cavity, and the torsion balance and for a spatial parameter 10–12 cm, the ultimate attainable sensitivity in the parameter exceeds the present level by roughly a factor of 10⁵.     

The ε-phase in rapidly solidified ferrous alloys

An Fe-1.9 wt% Si-4.2 wt% C alloy has been rapidly quenched from the melt in a controlled-atmosphere gun splat-cooling device to produce material consisting predominantly of the hexagonal close-packed-phase. The techniques of X-ray diffraction, scanning and transmission electron microscopy, and differential thermal analysis have been used to study the nature of the-phase and its decomposition during heat treatment. The presence of the metastable-phase could not be accounted for as the transformation product of a low stacking-fault energy austenite, and it appears to be formed directly from the liquid state. It has a complex and variable microstructure, which ranges from elongated, relatively featureless grains in the most rapidly-cooled areas to highly-faulted and twinned structural units containing precipitate particles. The-phase undergoes a two-stage decomposition process upon heating, but the first stage does not appear to involve the formation of martensite and-carbide, which has been the hitherto accepted reaction. As an alternative it is suggested that the-phase may decompose by a spinodal reaction.