Experimental study and mathematical modelling of a new of vibro-impact moling device

In this paper experimental study and mathematical modelling of newly designed vibro-impact moling rig are presented. The design is based on electro-mechanical interactions of a conductor with an oscillating magnetic field. The rig consists of a metal bar placed within a solenoid which is connected to an RLC circuit, and an obstacle block positioned nearby. Both the solenoid and the block are attached to a base board. Externally supplied alternating voltage causes the bar to oscillate and hit the block resulting in the forward motion of the base board mimicking a mole penetration through the soil. By varying the excitation voltage and the capacitance in the circuit, a variety of system responses can be obtained.In the paper the rig design and experimental procedure are explained in detail, and the mathematical modelling of the rig is described. Then the obtained coupled electro-mechanical equations of motion are integrated numerically, and a comparison between experimental results and numerical predictions is presented.     

Development and critical comparison of greener flow procedures for nitrite determination in natural waters

Two greener procedures for flow-injection spectrophotometric determination of nitrite in natural waters were developed and critically compared. Replacement of toxic reagents, waste minimization and treatment were exploited to attend the standards of clean chemistry. The flow system was designed with solenoid micro-pumps in order to minimize reagent consumption and waste generation. The first procedure is based on the Griess diazo-coupling reaction with sulfanilamide and N-(1-naphthyl)ethylenediamine (NED) yielding an azo dye, followed by photodegradation of the low amount of waste generated based on the photo-Fenton reaction. The second procedure is based on the formation of iodine from nitrite and iodide in acid medium in order to avoid the use of toxic reagents. For Griess method, linear response was achieved up to 1.0 mg L^− 1, described by the equation A = − 0.007 + 0.460C (mg L^− 1), r = 0.999. The detection limit was estimated as 8 μg L^− 1 at the 99.7% confidence level and the coefficient of variation was 0.8% (n = 20). The sampling rate was estimated as 108 determinations per hour. The consumption of the most toxic reagent (NED) is reduced 55-fold and 20-fold in comparison to batch method and flow injection with continuous reagent addition, respectively. A colorless residue was obtained by in-line photodegradation with reduction of 87% of the total organic carbon content. The results obtained for natural water samples were in agreement with those achieved by the reference method at the 95% confidence level. For the nitrite–iodide method, linear response was observed up to 2.0 mg L^− 1, described by the equation A = − 0.024 + 0.148C (mg L^− 1), r = 0.999. The detection limit was estimated as 25 μg L^− 1 at the 99.7% confidence level and the coefficient of variation was 0.6% (n = 20). The sampling rate was estimated as 44 determinations per hour. Despite avoiding the use of toxic reagents, the nitrite–iodide method presented worst performance in terms of selectivity and sensitivity.     

A multicommuted stop-flow system employing LEDs-based photometer for the sequential determination of anionic and cationic surfactants in water

It has been developed an automatic stop-flow procedure for sequential photometric determination of anionic and cationic surfactants in a same sample of water. The flow system was based on multicommutation process that was designed employing two solenoid micro-pumps and six solenoid pinch valves, which under microcomputer control carry out fluid propelling and reagent solutions handling. A homemade photometer using a photodiode as detector and two light emitting diodes (LEDs) with emission at 470 nm (blue) and 650 nm (red) as radiation sources, which was tailored to allow the determination of anionic and cationic surfactants in waters. The procedure for anionic surfactant determination was based on the substitution reaction of methyl orange (MO) by the anionic surfactant sodium dodecylbenzene sulfonate (DBS) to form an ion-pair with the cetyl pyridine chloride (CPC). Features such as a linear response ranging from 0.35 to 10.5 mg L⁻¹ DBS (R = 0.999), a detection limit of 0.06 mg L⁻¹ DBS and a relative standard deviation of 0.6% (n = 11) were achieved. For cationic surfactant determination, the procedure was based on the ternary complex formation between cationic surfactant, Fe(III) and chromazurol S (CAS) using CPC as reference standard solution. A linear response range between 0.34 and 10.2 mg L⁻¹ CPC (R = 0.999), a detection limit of 0.05 mg L⁻¹ CPC and a relative standard deviation of 0.5% (n = 11) were obtained. In both cases, the sampling throughput was 60 determinations per hour. Reagents consumption of 7.8 μg MO, 8.2 μg CPC, 37.2 μg CAS and 21.6 μg Fe(III) per determination were achieved. Analyzing river water samples and applying t-test between the results found and those obtained using reference procedures for both surfactant types provide no significant differences at 95% confidence level.     

A strip-shield improves the efficiency of a solenoid coil in probes for high-field solid-state NMR of lossy biological samples

A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800 MHz ¹H/¹⁵N and ¹H/¹³C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers.     

Multi-pumping in flow analysis: concepts, instrumentation, potentialities

A novel strategy for the implementation of flow-based analytical procedures using several micropumps is proposed. The pumps are switched individually or in combination, in order to create a pulsed flowing stream through the analytical path, and are the only active devices acting simultaneously as liquid propelling units, sample insertion ports and commuting elements. Configuration and control of the flow system are then greatly simplified. The micropumps produce distinct stroke volumes at distinct pulse frequencies with high reproducibility ensuring the attainment of very stable flow rates. This leads to an enhanced versatility that enables the utilisation of different approaches for sample management including step-wise variable sample volume, binary sampling and merging zones without reconfiguration of the system hardware. In contrast to the typical flow systems, the proposed one is characterised by a pulsed flow ensuring a fast sample/reagent mixing that contributes to improve the reaction development—thus sensitivity—even in situations of limited dispersion. The basic features and the performance of the proposed strategy are evaluated in the spectrophotometric determination of Cr(VI) in natural waters with 1,5-diphenylcarbazide.     

等离子体电磁加速器中快速电磁阀气体注入特性研究

在注气持续时间短、注入气体质量大的快速电磁阀测量中,采用高频响应压力传感器在电磁阀出口测量了气体的动态压力,通过真空室注气前后的压强差测量了注入气体的质量。研究表明,驱动电流、位移限定以及背景气压对气体注入特性有显著影响。当阀片受到的电磁力远大于背景气压造成的阻力时,增大驱动电流和增大背景气压都会加速流道口气体流动,提高气体注入量;电磁阀最高流速超过当地声速,流道应该设计成扩张式,且流道的长度要求尽可能短;电磁阀的注气持续时间主要由阀片的运动时间以及阀片关闭后气体在流道内扩散速率决定的。     

Single reaction interface in flow analysis

The dual or multiple reaction interface concept, commonly associated to the distinct flow techniques, was replaced by a single interface concept, which do not no rely on the utilisation of a well-defined and compelling sample volume but only on mutual penetration of sample and reagent zones at a single reaction interface where both sample and reagent met together prior to detection. In the proposed approach basic principles of flow analysis, such as controlled dispersion and reaction zone formation, are not influenced by sample and reagent volumes but determined exclusively by the extension of the overlap of two adjoining quasi-infinite zones enhanced by multiple flow reversals and the pulsed nature of the flowing streams.The detector is positioned at the core of the flow manifold (not in the conventional terminal position), and repetitive flow reversals enable interface manipulations, including multi-detection of the entire reaction interface or the monitoring of the evolution of a pre-selected interface zone by using suitable reversal cycle times.The implementation of the developed approach was facilitated due to the configuration simplicity and operational versatility of multi-pumping flow systems. Its performance was evaluated by monitoring processes involving two or four-solution reaction interfaces.     

Simulation on the response of new phosphate glass RPC for <Emphasis Type="Italic">γ</Emphasis>-rays and e<Superscript>+</Superscript>/e<Superscript>−</Superscript> particles using GEANT3

The influence of phosphate glass electrode in the configuration of resistive plate chamber has been studied using GEANT3.21 Monte Carlo code. Bakelite electrodes were replaced by phosphate glass electrodes, as these glass materials have low bulk resistivity, are portable and easy to handle. These types of RPCs in their compact form of all materials are suitable for high rate background environment. We find that these new types of RPCs give little higher response to γ-rays and e⁺/e⁻ particles, both for single-and double gap RPCs. The results of simulation are discussed.      

The Teichmüller distance between finite index subgroups of $${PSL_2(\mathbb{Z})}$$

For a given , we show that there exist two finite index subgroups of which are -quasisymmetrically conjugated and the conjugation homeomorphism is not conformal. This implies that for any there are two finite regular covers of the Modular once punctured torus T ₀ (or just the Modular torus) and a -quasiconformal map between them that is not homotopic to a conformal map. As an application of the above results, we show that the orbit of the basepoint in the Teichmüller space T(S ^p ) of the punctured solenoid S ^p under the action of the corresponding Modular group (which is the mapping class group of S ^p [6], [7]) has the closure in T(S ^p ) strictly larger than the orbit and that the closure is necessarily uncountable.      

Nonlinear mathematical modeling of butterfly valves driven by solenoid actuators

This paper describes high fidelity modeling and analysis of the opening and closing processes of butterfly valves driven by solenoid actuators using multiphysics models. The equations are derived and solved numerically. The variable of primary interest is the butterfly valve rotation angle. The coupled model for electromagnetics, fluid dynamics and mechanical dynamics are derived by making some simplifying assumptions. It is shown that the behavior of hydrodynamic torque plays an important role in the closing and opening processes. A discussion is presented with an explanation of the results and a comparison has been made for both the processes.