On built-in test techniques in reliable computer systems

Reliability is a primary criterion in the design of computer systems both from the points of view of fault tolerance and of repair, but the major difference lies in the relative cost constraints. Built-in test (BIT) techniques exploit hardware redundancy to provide continuous on-line monitoring of computer performance. Hardware's declining cost makes these techniques attractive, especially for modular computers. For both users and designers, it is important to understand the potential effectiveness of BIT approaches in terms of cost and performance. To assure BIT effectiveness, a computer BIT approach that supports the applicable system maintenance concepts must be selected, and required integral testing resources must be identified. This paper summarises present BIT approaches, discusses systematic ways to incorporate BIT into new computer designs and describes techniques for assessing BIT effectiveness in modular digital computers.     

MEMS加速度计在膛压测试中的应用

针对火炮膛压测试的特点,采用MEMS加速度计MMA8453Q和MSP430单片机研制了一种新的膛压测试系统。实现了单个芯片的存储测试,具有倒置上电,红外收发等功能。利用ANSYS对电路模块的缓冲特性进行了仿真分析,并利用马谢特锤对测试系统进行了抗过载测试。结果表明:在受到4.5×104gn冲击后仍能正常工作,满足火炮等高冲击场合的测试要求。     

燃烧室形状对柴油机压缩冲程影响的数值模拟

为研究柴油机燃烧室形状对柴油机压缩冲程的影响,应用计算流体力学(Computational Fluid Dynamics,CFD)数值方法,针对3种不同几何形状的直喷型柴油机燃烧室压缩冲程进行三维流场计算.计算结果表明缩口燃烧室具有较大的挤流强度和较合理的涡流分布,可以产生较高的缸内压力和温度,有利于混合气体的形成,与直口和敞口燃烧室相比性能较好.所采用的数值计算方法和分析结果对柴油机燃烧室的设计工作具有参考意义.     

Non-linear system identification using closed-loop data with no external excitation: The case of a lean combustion chamber

This paper deals with the analysis of a set of measurements collected on a lean premixed combustion process operating in a limit cycle. Due to the fact that the data are collected in closed-loop and the system has no external excitation, the identification task is particularly challenging. This work mainly focuses on the issue of the feasibility of the identification task. It will be shown that, despite the paucity of information available, a grey-box non-linear model can be estimated. The model provides an explanation both of the limit-cycle fundamental oscillation and of a non-harmonic high-frequency signal affecting the pressure of the combustion chamber.     

A sufficient condition to test identifiability of nonlinear delayed-differential models with constant delays and multi-inputs

In this paper, an original result in terms of a sufficient condition to test the identifiability of nonlinear delayed-differential models with constant delays and multi-inputs is given. The identifiability is studied for the linearized system and a criterion for linear systems with constant delays is provided, from which the identifiability of the original nonlinear system can be proved. This result is obtained by combining a classical identifiability result for nonlinear ordinary differential systems due to Grewal and Glover (1976) with the identifiability of linear delayed-differential models developed by Orlov, Belkoura, Richard, and Dambrine (2002). This paper is a generalization of Denis-Vidal, Jauberthie, and Joly-Blanchard (2006), which deals with the specific case of nonlinear delayed-differential models with two delays and a single input.     

电化学传感器测试富氢水中氢气体积分数的研究

提出利用复合电极测试富氢水中氢气体积分数的方法。试验表明:对于以2个铂丝分别作为工作电极和辅助电极,Ag/AgCl为参比电极的三电极体系,外部通以恒电位,工作电极维持在恒定的电位,可以实现敏感电极曲线。传感器对(0. 1～0. 8)×10-6体积分数的富氢水具有良好的传感性能,电化学传感器电流与氢气体积分数呈正比例线性关系,其响应时间低于5 s。     

Fault-containing self-stabilization in asynchronous systems with constant fault-gap

This paper presents a new transformation which adds fault-containment properties to silent self-stabilizing algorithms. The transformation features a constant slow-down factor and the fault-gap—that is the minimal time between two containable faults—is also constant. The transformation scales well to arbitrarily large systems and avoids global synchronization. The presented transformation is the first with a constant fault-gap and requires no knowledge of the system size.     

Multiway merge with constant delay in Concurrent Prolog

Multiway dynamic mergers with constant delay are an essential component of a parallel logic programming language. Previous attempts to defined efficient mergers have required complex optimising compilers and run-time support. This paper proposes a simple technique to implement mergers efficiently. The technique requires an additional data type and the definition of an operation on it. The operation allows multiple processes to access a stream without incurring the cost of searching for the end of stream. It is specified in Concurrent Prolog and is used to define multiple assignment variables using a monitor. The technique forms the basis for stream merging in Logix, a practical programming environment written in Flat Concurrent Prolog.     

Pole assignment in linear time-invariant multivariable systems with constant disturbances

Necessary and sufficient conditions are derived for a minimal order realizable, linear, time invariant differential feedback control system to exist for a linear time-invariant system with constant unknown disturbances, such that the eigenvalues of the closed-loop system take on pre-assigned values in the left hand part of the complex plane and such that the outputs of the system tend to zero as t → ∞. Some numerical examples are included to illustrate the result.     

Control of temperature uniformity in the temperature chamber with centrifugal acceleration

A novel method for control of temperature uniformity in the combined environmental testing is proposed. The structure of the temperature test chamber is introduced and the multi-input multi-output (MIMO) temperature control system is designed, in which the plant is approximated by the first-order plus time delay (FOPTD) model. The control objectives are summarized as making the average output temperature track the reference input and making the temperature at different spots track the average temperature. The controller is composed of two sub-controllers, each of which ensures the tracking performance of the average temperature and improves the uniformity of the temperature field, respectively. Both the simulation and experimental results show that the nonuniformity of the temperature field can be decreased effectively by the proposed method even if the temperature field is disturbed by centrifugal acceleration. The method provides an easy way to control the uniformity of the temperature field without decoupling and precise system identification.     

Experimental and numerical modeling of the effect of solid surface on NOx emission in the combustion chamber of a water heater

A combined experimental and CFD modeling study of the turbulent non-premixed natural gas on a laboratory scale has been performed. Effect of solid surface enhancement in combustion chamber on the flame temperature and NO emission was investigated. The solid surface called as filling material (FM) was cylindrical and was placed coaxially in the center of combustion chamber. The temperature and NO distribution in the combustion chamber were compared for different geometries of the filling material. The diameters of the filling materials were 25 and 30 cm with two lengths of 20 and 40 cm. Experimental study has been carried out on a fire tube water heater. The flame temperature on the center line of the combustion chamber, gas temperature and NO emission in the combustion chamber were measured. The actual geometry of the fire tube water heater and the burner were modeled and then analyzed by the FLUENT code. Turbulent diffusion flames were investigated numerically using a finite volume method for the solution of the conservation and reaction equations governing the problem. The measured values were specified as the boundary conditions. The elemental analysis of the natural gas was taken as a mixture of hydrocarbon and air was the oxidizer. The standard k-ε model was used for the modeling of the turbulence phenomena in the combustor. The non-premixed combustion model was chosen. In the conserved scalar approach, turbulence effects were accounted for with the help of an assumed shape probability density function or PDF. The discrete ordinates (DO) radiation model was used for modeling of the radiative heat transfer in the combustion room. The model results were compared with the experimental results. The model results were in good agreement with the measurements. The filling material provided the recirculation of the cooler gases into the flame. The recirculation reduced the oxygen concentration in the flame and controlled the flame temperature. It was found that the filling material with the diameter bigger than the flame diameter increased the heat transfer rate in the back flow around the flame.     

A miniaturized flow reaction chamber for use in combination with QCM-D sensing

A miniaturized flow chamber for quartz crystal microbalance with dissipation monitoring (QCM-D) has been developed. The main purpose was to reduce the total liquid sample consumption during an experiment, but also to gain advantages with respect to kinetics and mass transport by reducing the boundary diffusion layer. The bottom of the flow chamber is a QCM-D sensor surface, on which a polydimethylsiloxane spacer ring, fabricated onto a poly(methyl methacrylate) lid, is placed symmetrically around the QCM-D electrode (diameter ~10 mm). The spacer ring defines the inner chamber height (typically 40–50 μm) and provides sealing. Through the lid, there are inlet and outlet channels. The typical chamber volume is in the range of 2.5–3.5 μl (with a 10 μl dead volume). In flow mode, we have operated the cell at flow rates of 6–50 μl/min, i.e., volume turnovers of 2–17 per min. As a model system, to test the microcell, the formation of supported phospholipid bilayers on a SiO₂ surface was studied. For comparison, the same process was studied in a commercially available QCM-D equipment with significantly larger total volume (by a factor of 20). The decrease in effective sample consumption to produce a bilayer on the sensor surface in the chamber was approximately proportional to the decrease in chamber volume. Smaller volume also reduced the liquid exchange time. Potential improvements of the chamber include further optimization of the flow profile and, in addition, further miniaturization by decreasing the chamber height and the sensor radius.     

Molecular property correlation in alkanes with geometric volume

A large number of molecular and thermodynamic properties of the alkane molecules containing up to eight carbon atoms have been correlated with a newly developed theoretical index, geometric volume. The geometric volume gives an estimate of the molecular size and is characteristic of each alkane molecule. The n-alkanes generally show a smooth positive variation in their molecular properties with the geometric volume while the isomers correlate differently in many cases. In such cases, however, a single bilinear correlation equation may be derived for the entire set of alkane molecules. It is possible to obtain more realistic and meaningful correlation equations, if the regularities in the molecular properties of the alkane molecules are properly identified by graph theoretical ordering of the structure.     

Molecular property correlation in haloethanes with geometric volume

boiling point, melting point, density and refractive index of a variety of haloethanes have been correlated with a newly proposed theoretical index, geometric volume. Geometric volume offers an alternative scheme for the calculation of unit molecular volume. The validity of the concept has been tested by further correlation of geometric volume with molar volume (Mϱ) and critical volume (V_c). A new parameter, common volume, has been identified which is as effective as geometric volume in correlating the molecular properties in haloethanes.     

Cosmology in the Relativistic Theory of Gravitation with a positive cosmologic constant

In the framework of the Relativistic Theory of Gravitation, we consider a cosmological model which describes the known observational data, in particular, the accelerated expansion of the modern Universe. The dynamic equation contains a positive cosmological constant. The equations obtained describe an oscillating universe without singularities. Results of numerical calculations are presented.     

No interference of task complexity with circadian rhythmicity in a constant routine protocol

Time course in task performance has been studied extensively. In particular, the investigation of circadian rhythmicity in task performance that varied in complexity. However, these studies disclosed heterogeneous outcomes. This could be the result of confounding exogenous factors, the use of diverse tasks, as well as accumulating sleepiness interfering with the underlying circadian drive. The present study varied task demands systematically within a single task and a dual task, using a constant routine protocol to examine the unmasked influence of the endogenous circadian oscillator on the periodicity of performance. Moreover, the subjects were divided into an early-start and a late-start group to estimate the potential interaction of circadian rhythmicity with the duration of prior wakefulness. The results revealed a distinct congruence in the circadian rhythms of all performance measures, with which prior wakefulness (< 40 h) did not interact. Also, single-task as well as dual-task complexity did not interfere with circadian rhythmicity. In conclusion, when sufficiently controlled for masking exogenous factors, task complexity is removed from the underlying circadian rhythms.     

No interference of task complexity with circadian rhythmicity in a constant routine protocol

Time course in task performance has been studied extensively. In particular, the investigation of circadian rhythmicity in task performance that varied in complexity. However, these studies disclosed heterogeneous outcomes. This could be the result of confounding exogenous factors, the use of diverse tasks, as well as accumulating sleepiness interfering with the underlying circadian drive. The present study varied task demands systematically within a single task and a dual task, using a constant routine protocol to examine the unmasked influence of the endogenous circadian oscillator on the periodicity of performance. Moreover, the subjects were divided into an early-start and a late-start group to estimate the potential interaction of circadian rhythmicity with the duration of prior wakefulness. The results revealed a distinct congruence in the circadian rhythms of all performance measures, with which prior wakefulness (<?40?h) did not interact. Also, single-task as well as dual-task complexity did not interfere with circadian rhythmicity. In conclusion, when sufficiently controlled for masking exogenous factors, task complexity is removed from the underlying circadian rhythms.     

柴油机可调涡流比燃烧过程三维仿真

在柴油机进气歧管前安装蝶形涡流调节阀,通过调整直气道侧的有效流通面积改变缸内涡流强度。在稳流吹风试验平台,研究涡流调节阀角度对进气道流量因数和涡流比的影响,并结合粒子图像测速（particle image velocimetry,PIV）分析缸内涡流的形成过程。采用计算流体力学（computational fluid dynamics,CFD）评估涡流调节阀角度对缸内混合气体形成过程的影响,计算结果可复现三维 PIV测量的缸内流场结构和相似的涡心位置。随着进气门关闭,涡流比从0.57提高到2.05,油气在周向的相互作用增强,从而加速预混燃烧阶段的放热速度,促使燃烧重心提前、燃烧持续期缩短。在相同进气流量条件下,强涡流运动也促使累积放热量增加。     

Lattice-based signcryption with equality test in standard model

A signcryption, which is an integration of a public key encryption and a digital signature, can provide confidentiality and authenticity simultaneously. Additionally, a signcryption associated with equality test allows a third party (e.g., a cloud server) to check whether or not two ciphertexts are encrypted from the same message without knowing the message. This application plays an important role especially in computing on encrypted data. In this paper, we propose the first lattice-based signcryption scheme equipped with a solution to testing the message equality in the standard model. The proposed signcryption scheme is proven to be secure against insider attacks under the learning with errors assumption and the intractability of the short integer solution problem. As a by-product, we also show that some existing lattice-based signcryptions either is insecure or does not work correctly.     

Sampling and reconstruction of piecewise constant stochastic processes with Erlang stay time in states

A statistical sampling and reconstruction procedure is developed for the class of stochastic processes indicated in the title. The Erlang phase method and recurrent recalculation for conditional Markov processes are used. Formulas for the a posteriori distribution of the transition time are obtained for the respective first moments and sampling interval. The procedures are easy-to-implement computationally. The influence of process parameters on the procedure parameters is analyzed. An illustrative example is given.