Higher order sensing using QCM sensor array and preconcentrator with variable temperature

We proposed the higher order sensing method using a preconcentrator with variable temperature in combination with the quartz-crystal microbalance sensor array to extract many features of the samples. The temperature of the preconcentrator tube packed with hydrophobic adsorbent was gradually raised to 200/spl deg/C. The rough separation among the compounds along the time axis enhanced the discrimination capability of the sensor array system. The results of the second-order sensing, such as images of the sensor responses and the loci on the principal component analysis space, gave us information about the apple flavors with different recipes. Moreover, the low-concentration flavors, such as apple and banana in water, were successfully discriminated using the proposed method. It was found that the system was robust against the sample concentration change under the environment of the large humidity.     

Thermosiphon-based PCR reactor: experiment and modeling

A self-actuated, flow-cycling polymerase chain reaction (PCR) reactor that takes advantage of buoyancy forces to continuously circulate reagents in a closed loop through various thermal zones has been constructed, tested, and modeled. The heating required for the PCR is advantageously used to induce fluid motion without the need for a pump. Flow velocities on the order of millimeters per second are readily attainable. In our preliminary prototype, we measured a cross-sectionally averaged velocity of 2.5 mm/s and a cycle time of 104 s. The flow velocity is nearly independent of the loop's length, making the device readily scalable. Successful amplifications of 700- and 305-bp fragments of Bacillus cereus genomic DNA have been demonstrated. Since the device does not require any moving parts, it is particularly suitable for miniature systems.     

Microfluidic cell electroporation using a mechanical valve

A microfluidic electroporation technique is demonstrated based on the operation of an elastomeric valve in a poly(dimethylsiloxane) (PDMS) fabricated microchip and a common dc power supply. The pulse needed for permeabilization of the cell membrane is generated by temporarily interrupting the circuit using the valve. The electropermeabilization of suspended and adherent Chinese hamster ovary cells with green DNA dye SYTOX is demonstrated. The technique eliminates the cost and complexity associated with a pulse generator and microfabricated electrodes that are often involved in microscale electroporation devices. It also offers the potential of integrating electroporation as a unit operation in large-scale microfluidic systems with the increasing application of elastomeric valves in these systems.     

Microfluidic flow-flash: method for investigating protein dynamics

We report a new method, microfluidic flow-flash, for measuring protein reaction kinetics. The method couples a microscope imaging detection system with a microfluidic flow cell to reduce data acquisition times and sample consumption. This combination allows for the simultaneous collection of spectral and temporal information. The microfluidic flow cell design utilizes three-dimensional sheath flow to reduce sample dispersion and minimize sample consumption. The ability to alter the flow rates in the microfluidic flow cells allows a variety of time scales to be studied with submillisecond time resolution. The imaging detection system can be coupled with several spectroscopic probes including fluorescence and UV/visible absorbance spectroscopy. Here, we utilize the microfluidic flow-flash method to probe the kinetics of CO recombination or O2 binding to myoglobin after the laser-induced photolysis of CO from myoglobin by UV/visible absorbance spectral imaging.     

Parameter calibration and inadequacy modeling in a computer experiment

Deterministic simulation is a popular tool used to numerically solve complex mathematical models in engineering applications. These models often involve parameters in the form of numerical values that can be calibrated when real‐life observations are available. This paper presents a systematic approach in parameter calibration using Response Surface Methodology (RSM). Additional modeling by considering correlation in error structure is suggested to compensate the inadequacy of the computer model and improve prediction at untried points. Computational Fluid Dynamics (CFD) model for manure storage ventilation is used for illustration. A simulation study shows that in comparison to likelihood‐based parameter calibration, the proposed parameter calibration method performs better in accuracy and consistency of the calibrated parameter value. The result from sensitivity analysis leads to a guideline in setting up factorial distance in relation to initial parameter values. The proposed calibration method extends RSM beyond its conventional use of process yield improvement and can also be applied widely to calibrate other types of models when real‐life observations are available. Moreover, the proposed inadequacy modeling is useful to improve the accuracy of simulation output, especially when a computer model is too expensive to run at its finest level of detail. Copyright © 2011 John Wiley and Sons Ltd.     

Photothermal deflection in multilayer coatings: modeling and experiment

A model of the photothermal deflection signal in multilayer coatings is presented that takes into account optical interference effects and heat flow within the stack. Measurements are then taken of high-reflectivity HfO2/SiO2 ultraviolet mirrors made by plasma ion assisted deposition and compared to calculations. Good agreement is found between the experimental results and the model. Using this model for the calibration and the setup described, one can measure absorption in multilayer coatings accurately down to 10(-7) of the incident power.     

磁性液体阻尼减振器动力学建模及实验

提出了一种结构简单的磁性液体阻尼减振器。根据牛顿第二定律和液体的连续性方程,建立了减振器中磁性液体流动的动力学模型,结合弹性悬臂梁的振动能量,得到减振器施加于悬臂梁后梁对数衰减率的表达式。设计实验验证减振器中不同永磁体半径,外壳与永磁体间的不同间隙以及不同饱和磁化强度的磁性液体对梁振动对数衰减率的影响,表明在所假设的条件下,理论与实验结果的一致性较好。同时还发现,在一定的范围内,磁性液体阻尼减振器的阻尼效果随着永磁体半径的增大而增大;减振器外壳与永磁体间有一最佳间隙,可使得梁振动达到最大的对数衰减率。     

Nonlinear logistic regression mixture experiment modeling for binary data using dimensionally reduced components

This article motivates, presents, and illustrates an approach using nonlinear logistic regression (NLR) for modeling binary response data from a mixture experiment when the components can be partitioned into groups used to form dimensionally reduced components (DRCs). A DRC is formed from a linear combination of the components in a group having similar roles and/or effects of the same sign, where the linear combinations over all groups are normalized so that the DRC proportions sum to one. Linear combinations of a particular form provide for quantifying the effects of the remaining components in a group relative to a chosen component. This reason, plus dimensional reduction, are the primary motivations for the proposed DRC mixture experiment modeling approach. NLR is required because models expressed in terms of the DRCs are nonlinear in the parameters that specify the linear combinations. A method for obtaining nonparametric tolerance limits on the probability of a “success” for the binary response variable using a bootstrap approach is also presented. Finally, the article shows how DRCs provide for visualizing data and modeling results that otherwise would be impossible. A real database on the presence or absence of nepheline crystals in simulated nuclear waste glass is used to illustrate the NLR modeling and nonparametric tolerance limit approaches. The methodology is general and can be applied to other applications.     

Diffractive light trapping in crystal-silicon films: experiment and electromagnetic modeling

Diffractive light trapping in 1.5 μm thick crystal silicon films is studied experimentally through hemispherical reflection measurements and theoretically through rigorous coupled-wave analysis modeling. The gratings were fabricated by nanoimprinting of dielectric precursor films. The model data, which match the experimental results well without the use of any fitting parameters, are used to extract the light trapping efficiency. Diffractive light trapping is studied as a function of incidence angle, and an enhancement of light absorption is found for incidence angles up to 50° for both TE and TM polarizations.     

Reconstruction of a strip geometry calorimeter using stepwise regression

An algorithm used to reconstruct events in a 2.44 m by 4.88 m three view electromagnetic calorimeter is presented. The least-squares fitting technique, stepwise regression, was adapted to this pattern recognition problem so that many possible combinations of particle candidates could be considered quickly. The result is an optimal set of particle candidates along with their positions and energy deposits.     

Steady thermal contact of a half strip and a strip

The steady temperature field of a strip and a half strip connected at one end but with different thermophysical properties is determined for mixed conditions in the contact region.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 2, pp. 302–307, August, 1987.     

High Q metal strip SSBW resonators using a SAW design

An experimental study of metal strip surface skimming bulk wave (SSBW) resonators using a surface acoustic wave (SAW) design is presented. Characteristics of SSBW and SAW resonators fabricated with the same photolithographic mask are compared and discussed. High Q low-loss SSBW resonators are achieved using a conventional two-port SAW resonator design and taking special care of the distance L between both interdigital transducers, the metal thickness h/lambda (lambda=acoustic wavelength) and the finger-to-gap ratio. Best overall performance of the SSBW devices in this study is achieved at L=nlambda/2-lambda/4 (compared with L=nlambda/2-lambda/8 for SAW resonators), h /lambda=1.6% (compared with 2% for SAW), and finger-to-gap ratio close to 1. The best device fabricated shows an unloaded Q of 5820 and an insertion loss of 7.8 dB at 766 MHz. The SSBW resonant frequency shows a stronger dependence on the metal thickness than the SAW one. This problem, however, is readily solved by frequency trimming using a CF(4) plasma etching technique. SSBW resonator can be trimmed by 0.2% down in frequency (compared with 0.05% for SAW) without affecting their performance.     

Aggregate versus disaggregate production planning: a simulated experiment using LDR and MRP

Within the past several years, considerable research has been devoted to the aggregate production planning problem starting with the pioneering work of Holt el al, (1955) and the resulting Linear Decision Rule (LDR). However, researchers have also recognized that developing optimal aggregate production plans, per se, is not sufficient for solving real problems; these plans have to be disaggregated into specific schedules for specific products. Consequently, the thrust of current research is on the ‘disaggregation’ problem. Simultaneously a number of companies have been installing MRP systems with reports of significant improvements in inventory control, production planning, work force scheduling and production costs. This paper reports on an experiment which was designed and conducted to compare the effectiveness of the ‘aggregate-disaggregate’ and MRP approaches to production planning in a simulation environment. LDR was used as the optimal aggregate technique in the aggregate-disaggregate approach. The results appeared to favour the MRP approach     

Dielectric constant measurement technique for a dielectric strip using a rectangular waveguide

A dielectric constant measurement technique for dielectric strips is presented in this paper. In the measurement, the strip is placed parallel to the broad walls of a rectangular waveguide, and it is found that the measured reflection coefficient is insensitive to the position of the strip when it is placed around the middle of the waveguide cross section. The new sample placement scheme becomes very convenient, especially when a large number of strips have to be measured. To develop the forward scattering formulation, the reflection coefficient of the strip placed in the waveguide is evaluated using the method of moments. With this forward model, a genetic algorithm is developed to retrieve the dielectric constant of the strip from the measured reflection coefficient. The validity of the calculated reflection coefficient is verified by measuring a Teflon strip in a WR187 waveguide, and the dielectric constant of the Teflon is successfully retrieved from the measurement. For the measurement of many strips, a special sample holder is made to ensure insensitivity of the measured reflection coefficient to the position of the strip.     

Static analysis of diaphragm-supported cylindrical shells using a curved finite strip

Two versions are presented of a tranversely-curved finite strip for the static analysis of circular cylindrical shells. The strip is a refined displacement model with sixteen transverse degrees-of-freedom arranged either at two or at four nodal lines. The analysis is specialized for cylinders with diaphragm supports at the ends—via the employment of simple trigonometric series in the longitudinal direction—but extension to other end conditions is straightforward in principle. Detailed results of applications of the curved strip are presented.     

Highly selective and sensitive electrochemical detection of dopamine using a nafion coated hybrid macroporous gold modified electrode with platinum nanoparticles

A coral-like macroporous Au electrode with electroplated Pt nanoparticles (hybrid macroporous Au-/nPts) coated with Nafion has been fabricated for the first time and used for highly selective and sensitive determination of dopamine (DA). The physically characterized results indicated that the electroplated Pt nanoparticles were dispersed uniformly on the macroporous Au electrode. The porosity and window pore size of the fabricated macroporous Au electrode were 50% and 100-300 nm, respectively. Also the electroplated Pt nanoparticles size was approximately 10-20 nm. The cyclic voltammograms results showed that the hybrid macroporous Au-/nPts exhibited a much larger surface activation area, a roughness factor (RF) of 2024.7, much higher than that of the macroporous Au electrode, which is 46.07. The electrochemical experimental results showed that the hybrid macroporous Au-/nPts coated with Nafion exhibited a dramatic electrocatalytic effect on the oxidation of DA. At 0.1 V, it responded linearly to DA concentrations ranging from 20 μ M to 160 μ M with a detection sensitivity of 90.9 μA mM (-1) cm (-2). Furthermore, it showed wide detection ranging from 20 nM to 900 μ M. At the same time, the interference of ascorbic acid (AA) was effectively avoided because of the Nafion film coated on the surface of the hybrid electrode.     

Improving WC-Co coating adhesive strength on rough substrate:Finite element modeling and experiment

The adhesive strength in a coating-substrate system is of primary importance for the coating lifetime in service. However, the underlying mechanism is not fully understood due to the complex internal structure of composite coatings. In this study, the effect of substrate roughness on the adhesive strength of WCCo coatings was investigated by experiment and simulation. Results show that the adhesive strength is significantly affected by the roughness. In the case of the Ra2 μm, the adhesive strength is approximately 35–46 MPa. When the Ra is 4 μm, the adhesive strength increases to nearly 60 MPa. A finite element model was developed to correlate the roughness with adhesive strength. It is found that the predicted values are well consistent with the experimental data. In addition, with the increase of the roughness,the residual stress would be changed from concentrated state to widespread state, which decreases the critical stress to result in crack propagation. That's why a larger roughness can cause a higher adhesive strength. This study gives understanding on the mechanism of adhesive strength affected by roughness,which contributes to the parameter optimization with better performance.     

Empirically modeling polymer collapse in a poor solvent via a non-equilibrium,granular chain experiment

We present a new empirical method for investigating the collapse of a semi-flexible, homogeneous polymer-like structure in a poor solvent. A stainless steel chain in a thin film of water that is vertically oscillated plays the role of the polymer in our model system. As the system is shaken, the chain collapses into a steady-state compact configuration. Collapse is largely dominated by the surface tension of the water; however other factors also contribute in a one-to-one correspondence with real homopolymers. This system may be tailored to investigate the physics of polymer folding in a fundamental manner. We use the normalized radius of gyration to compare collapse dynamics between experiments of different chain lengths. Free energy minimizing behavior is observed as the polymer passes through both “on-pathway” and “off-pathway” intermediate states. At all chain lengths, nucleation (formation of pearls) dominates the early stage of collapse dynamics. If the ends of the chain remain within the radius of gyration, collapse occurs quickly. However, when the ends of the chain stray far outside the radius of gyration, nucleation is impeded and collapse progresses more slowly.     

Measurement of the strength of a pulsed electromagnetic field using a strip transmission line

Theories, proposed in previous publications, are used to calculate the currents in the loads of a linear stripline transducer for different versions of its loading and orientation. The results of a comparison of experimental investigations and the calculation are given.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 56–60, November, 1993.