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The downward continuation of potential fields is a process of calculating their values in a lower plane based on those of a certain plane. This technology is not only a data processing method for resource exploration but also plays an extremely important role in military applications. However, the downward continuation of potential fields is a typical linear inverse problem that is ill-posed. Generalized minimal residuals (GMRES) is an effective solution to ill-posed inverse problems, but it is unstable under the condition wherein the GMRES is directly applied in the calculation process. Moreover, the long-term behavior of its iterative computation is a disordered, divergent result. Therefore, to obtain stable solutions, GMRES is applied to solve the normal equations of the downward continuation of potential fields; it is also used to prequalify for occasional interruptions in the operation process by adding the damping coefficient, thus strengthening the stability conditions of the equations of residual minimization. Finally, the stable downward continuation of the potential fields method is proposed. As indicated by the theoretical data and the measured testing data, the method proposed in this paper has the advantages of high-precision and excellent stability. Furthermore, compared with the Tikhonov iteration method, the proposed method avoids the need to choose regularization parameters.

An optimization strategy combining computational fluid dynamics (CFD) with multiobjective evolutionary algorithm (MOEA) for dual-impeller design in an aerated tank was proposed to maximize the overall effective gas holdup and minimize the power consumption with six geometrical variables. The nondominated sorting genetic algorithm-II (NSGA-II) was applied to construct a Pareto front from numerous design points with greatly reduced computation. The measurement of local gas holdup and power consumption by dual electric conductivity probe and torque sensor was utilized to verify the CFD model and evaluate the optimal design. The optimal design with a pitched concave blade disk turbine as the lower impeller and a down-pumping pitched blade turbine as the upper impeller exhibited the best gas dispersion performance with efficient energy savings. This approach has the potential to greatly enhance the efficiency of industrial stirred reactors.

A gold nanospheres (Au NSs)-enhanced photoacoustic (PA) system has been developed to detect parts per trillion (ppt)-level mercury ion (Hg2+) in aqueous environments, which combines the advantages of the high sensitivity of PA detection and high extinction coefficient of Au NSs. 4-mercaptophenylboronic acid (MPBA) is used as the aggregation agent to detect Hg2+ by a designed PA system. Experimental results demonstrate a linear relationship between the amplitude of PA signals and logarithmic concentration of Hg2+ in the range of 10 pM-1 μM (R=0.994). The detection limit of this Au NSs-enhanced PA system is 78 pM (16 ppt, S/N=3) with a quick response time of 1 min. This method has excellent selectivity for Hg2+ over other heavy metal ions, alkali, and alkaline earth metal ions. The system is cost-effective and shows a great potential for quick detection of Hg2+ trace in water with very high sensitivity.

Stereoscopic display is a standard display mode for virtual reality environments. Typical 3D projection provides only a single stereoscopic video stream; thus co-located users cannot correctly perceive the virtual scene based on their own position and view. Several works devoted to developing multi-user stereoscopic display, but the number of users is very limited or the technical implementation is complicated. In this paper we put forward two flexible and simple projection-based multi-user stereoscopic display systems. The first one, named TPA, is based on a triple-projector array and provides a 120Hz active stereo for three users. Two TPAs can be combined to form a six-user system. The second one, named DPA, is a dual-projector and easy-implemented system providing individual stereoscopic video stream for two to six users. Finally, a co-located multi-user virtual fireman simulation training system and a virtual tennis simulation system were created to verify the effectiveness of our systems.

In this paper, we present a method of view-dependent stereoscopic projection on curved screen. It allows the user to walk around with the correct perspective view of the virtual scene consistent with his/her location. To solve the problem of distortion and drift of virtual objects when projecting the view-dependent scene images on curved screen, we operate a dynamic parallax adjustment of the stereoscopic images according to viewpoints. User evaluation shows that our proposed approaches are effective on improving visual experience.

Diabetes mellitus (DM) is worldwide health concern whose complication leads to death. Stabbing finger as prevalent monitoring method brings pain and risk of infection to the patient. Photoacoustic technique is employed to determinate the concentration of blood glucose non-invasively due to its advantage of avoiding the disturbance of optical scattering. But until now there is still no breakthrough on non-invasive blood glucose determination. The problem is that there is not only glucose in human blood but also a lot of other interference elements such as protein, fat and so on. These elements could interfere determination and cause accurate and useful information lost. To solve this problem, we proposed a new approach: using 2 dimension spectrum of photoacoustic extracting multi information of photoacoustic signal which mean combing optical spectrum and sound spectrum. This could improve the specificity and accuracy of detection. This paper describes the theory of photoacoustic and the dual-spectral method of photoacoustic. The experiment system is built to verify the 2 dimension spectrum method used in concentration determination. The experiment result shows that dual-spectrum of photoacoustic method can realize non-invasive photoacoustic blood glucose measurement.

Noninvasive blood glucose determination has received considerable attention in the past from both patients and scientists all over the world, and it is becoming increasingly important as a research focus. The two most difficult problems leading to no breakthrough in this area are sensitivity and specificity in determination. In order to obtain reliable measurement results of blood glucose levels, we propose a new liquid photoacoustic resonance theory that can significantly enhance the intensity of the signal and improve the sensitivity. This paper demonstrates the theory of liquid photoacoustic resonance, gives a rigorous mathematical expression, and analyzes the variation of the transducer output in the case of liquid photoacoustic resonance. A signal processing method is demonstrated at the same time under the liquid photoacoustic resonance condition. Meanwhile, the feasibility and validity are verified by experiments with different concentrations of glucose solution. The result shows that liquid photoacoustic resonance can strengthen the signal, and the resolution achieves 20 mg/dL. This method overcomes the issue of low sensitivity and the inaccurate detection in the nonresonant case, and gets accurate results. This result could provide a theoretical basis for realization of noninvasive measurement of blood glucose.

Diabetes mellitus (DM) is a chronic disease affecting nearly 400 million people worldwide. In order to manage the disease, patients need to monitor the blood glucose level by puncturing the finger several times a day, which is uncomfortable and inconvenient. We present here a potential non-invasive monitoring method based on the velocity of ultrasonic waves generated in glucose solution by the photoacoustic principal, which can recognize the glucose concentration down to 20mg/dL. In order to apply this method to warm bodies, we carefully designed the experiment and performed measurements from 30 °C to 50 °C to generate a set of calibration curves, which may be used by engineers to build devices. Most importantly, we have theoretically explained the relationship between the compressibility and the glucose concentration. Our results show that the compressibility of solution decreases with the glucose concentration, which clarified the controversy between theory and experiment results in the literature. The derived formula is generally validity, which can be used to nondestructively measure solution concentration for other types of solutions using photoacoustic principle.

Methanol conversion time dependent selectivity is suggested for the kinetic characterization of zeolite pore architecture and acidic properties. The reaction has been investigated with the zeolites HZSM5 and HUSY as a function of duration of experiment at various temperatures. Four kinetic regimes are distinguished: Autocatalysis, retardation, reanimation and deactivation. Deactivation at 475 o C allows to discriminate coking via acid catalysis from coking via radical-like conversion of methanol. It is concluded, that HZSM5 deactivates at this temperature through growth of coke seeds on the crystallite surface and coverage of the pore entrances. The deactivation of HUSY proceeds differently: a primary acid site deactivation with “olefin coke” and a secondery filling of the pore system with “methanol coke”.

Methanol has been converted to mainly hydrocarbons and water on four different acidic catalysts at 375 and 475 °C, WHSV of o. 1 and 1 h −1 and the time on stream selectivity changes have been studied in detail. Results are preferentially presented as a function of normalized time on stream. The propane/propene ratio is taken as a measure of catalyst activity. Yields of coke, CO + CO 2 , selectivity of formation of methane, C 2 -C 5 -HC'S and aromatic HC's are preferentially regarded. The time on stream selectivity changes allow conclusions about the nature of individual reaction steps and discrimination of the dynamic systems pertinent for H-ZSM-5. H-Mordenite, RE-Y and a Durabead-I catalyst sample.

The changes in detailed product composition with proceeding time on stream have been studied during methanol conversion on H-ZSM-5, RE-Y, H-mordenite and an amorphous silica/alumina catalyst. In parallel experiments the build up of coke has been determined. Results are comparatively evaluated as a function of “Normalized Time on Stream” (NTOS). Catalyst deactivation is kinetically traced with the help of the propane/propene mole ratio and exhibits different deactivation patterns for the examined catalysts. One type of deactivation-slow deactivation in the range NTOS = 0 to 0.5 and fast deactivation in the range NTOS = 0.5 to 1.0 is explained as resulting from mass transport limitations respectively filling of the pore volume with organic deposites (e. g. H-ZSM-5 and RE-Y at 375 °C). A second type of deactivation-fast deactivation in the range NTOS = 0 to 0.5 and slow deactivation in the range NTOS = 0.5 to 1.0 is related to specific deactivation of the active catalyst sites and observed e. g. at high temperature (475 °C) with RE-Y. As one prominent reaction of coke formation from methanol the direct non catalytic alkylation of coke has been observed. As a typical reaction which lowers the hydrogen content of the coke at elevated temperature the formation of methane has been found. The influences of geometric constraints (shape selectivity) and acidity of the catalyst on individual reaction steps in the reactions network are established from the selectivity results. The deposited coke participates in the overall conversion. The reduced coke selectivity, which is obtained with H-ZSM-5, and its special nature (mainly two ring aromatics have been found) are the reason for inhibition of several important reaction steps, particularly the formation of methane and H2 plus CO.