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Feb 2011

Volume 82, Issue 2, Articles (02xxxx)

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back to top General Instruments

A constant-speed lowering mechanism for the crucibles

S. Bangaru and G. Muralidharan

Rev. Sci. Instrum. 82, 025101 (2011); http://dx.doi.org/10.1063/1.3527060 (5 pages)

Online Publication Date: 1 February 2011

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The crystal growth characteristics of a certain material can be considerably influenced by the strain present in the growing crystal. Strain can be induced in various ways. One of the most common methods always presents in industrial processes, where attrition processes are always accompanied by generation of mechanical strain in a newly formed small crystal fragment obtained by mechanical stressing during preparation and handling. For this purpose, we have developed an apparatus which comprises a specially designed constant, special lowering device. The system was constructed for use with a Bridgeman furnace made in the laboratory for the crystal growth. The apparatus has been used with a variety of growth assemblies to grow crystals of materials with melting points in the range of 100–1000°C.
Show PACS
81.10.Fq Growth from melts; zone melting and refining
81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.20.mm Fracture
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

High-throughput measurement of rice tillers using a conveyor equipped with x-ray computed tomography

Wanneng Yang, Xiaochun Xu, Lingfeng Duan, Qingming Luo, Shangbin Chen, Shaoqun Zeng, and Qian Liu

Rev. Sci. Instrum. 82, 025102 (2011); http://dx.doi.org/10.1063/1.3531980 (7 pages) | Cited 7 times

Online Publication Date: 7 February 2011

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Tillering is one of the most important agronomic traits because the number of shoots per plant determines panicle number, a key component of grain yield. The conventional method of counting tillers is still manual. Under the condition of mass measurement, the accuracy and efficiency could be gradually degraded along with fatigue of experienced staff. Thus, manual measurement, including counting and recording, is not only time consuming but also lack objectivity. To automate this process, we developed a high-throughput facility, dubbed high-throughput system for measuring automatically rice tillers (H-SMART), for measuring rice tillers based on a conventional x-ray computed tomography (CT) system and industrial conveyor. Each pot-grown rice plant was delivered into the CT system for scanning via the conveyor equipment. A filtered back-projection algorithm was used to reconstruct the transverse section image of the rice culms. The number of tillers was then automatically extracted by image segmentation. To evaluate the accuracy of this system, three batches of rice at different growth stages (tillering, heading, or filling) were tested, yielding absolute mean absolute errors of 0.22, 0.36, and 0.36, respectively. Subsequently, the complete machine was used under industry conditions to estimate its efficiency, which was 4320 pots per continuous 24 h workday. Thus, the H-SMART could determine the number of tillers of pot-grown rice plants, providing three advantages over the manual tillering method: absence of human disturbance, automation, and high throughput. This facility expands the application of agricultural photonics in plant phenomics.
Show PACS
89.20.Kk Engineering
88.20.df Food crops

Application of stochastic system identification to the study of the compliance of electroactive polymers

Priam V. Pillai, Ian W. Hunter, and Emanuel Hernandez

Rev. Sci. Instrum. 82, 025103 (2011); http://dx.doi.org/10.1063/1.3523054 (6 pages)

Online Publication Date: 11 February 2011

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Electroactive polymers have shown promising applications as transducers that can mimic biological muscle. The modulus or the compliance of many of these devices can change significantly as they are actuated making these materials attractive for applications that require tunable stiffness. We have developed a dynamic mechanical analyzer that is capable of making in situ measurements of the dynamic compliance transfer function of conducting polymers as a function of an electrochemical stimulus. We do this by simultaneously applying a stochastic stress waveform over a potential waveform and calculating the compliance as it changes over the course of electrochemical excitation. Using these signals we can calculate the compliance transfer function between 0.1 and 100 Hz and the impulse response function with up to 3% variation in its parameters. These functions are then computed as charge is injected into the polymer and it is shown that the low frequency gain of the transfer function can change by 30%–40% in the electrochemical system tested.
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42.70.Jk Polymers and organics
87.80.Kc Electrochemical techniques
FREE

Rapid consolidation of powdered materials by induction hot pressing

Aaron D. LaLonde, Teruyuki Ikeda, and G. Jeffrey Snyder

Rev. Sci. Instrum. 82, 025104 (2011); http://dx.doi.org/10.1063/1.3534080 (4 pages) | Cited 13 times

Online Publication Date: 15 February 2011

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A rapid hot press system in which the heat is supplied by RF induction to rapidly consolidate thermoelectric materials is described. Use of RF induction heating enables rapid heating and consolidation of powdered materials over a wide temperature range. Such rapid consolidation in nanomaterials is typically performed by spark plasma sintering (SPS) which can be much more expensive. Details of the system design, instrumentation, and performance using a thermoelectric material as an example are reported. The Seebeck coefficient, electrical resistivity, and thermal diffusivity of thermoelectric PbTe material pressed at an optimized temperature and time in this system are shown to agree with material consolidated under typical consolidation parameters.
Show PACS
81.07.Wx Nanopowders
72.80.-r Conductivity of specific materials
66.30.Xj Thermal diffusivity
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.43.Gt Powders, porous materials

The Twente turbulent Taylor–Couette (T3C) facility: Strongly turbulent (multiphase) flow between two independently rotating cylinders

Dennis P. M. van Gils, Gert-Wim Bruggert, Daniel P. Lathrop, Chao Sun, and Detlef Lohse

Rev. Sci. Instrum. 82, 025105 (2011); http://dx.doi.org/10.1063/1.3548924 (13 pages) | Cited 6 times

Online Publication Date: 16 February 2011

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A new turbulent Taylor–Couette system consisting of two independently rotating cylinders has been constructed. The gap between the cylinders has a height of 0.927 m, an inner radius of 0.200 m, and a variable outer radius (from 0.279 to 0.220 m). The maximum angular rotation rates of the inner and outer cylinder are 20 and 10 Hz, respectively, resulting in Reynolds numbers up to 3.4 × 106 with water as working fluid. With this Taylor–Couette system, the parameter space (Rei, Reo, η) extends to (2.0 × 106, ±1.4 × 106, 0.716−0.909). The system is equipped with bubble injectors, temperature control, skin-friction drag sensors, and several local sensors for studying turbulent single-phase and two-phase flows. Inner cylinder load cells detect skin-friction drag via torque measurements. The clear acrylic outer cylinder allows the dynamics of the liquid flow and the dispersed phase (bubbles, particles, fibers, etc.) inside the gap to be investigated with specialized local sensors and nonintrusive optical imaging techniques. The system allows study of both Taylor–Couette flow in a high-Reynolds-number regime, and the mechanisms behind skin-friction drag alterations due to bubble injection, polymer injection, and surface hydrophobicity and roughness.
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47.27.-i Turbulent flows
47.32.Ef Rotating and swirling flows
47.50.-d Non-Newtonian fluid flows
47.55.D- Drops and bubbles
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.85.lb Drag reduction

High pressure cell for neutron reflectivity measurements up to 2500 bar

Christoph Jeworrek, Roland Steitz, Claus Czeslik, and Roland Winter

Rev. Sci. Instrum. 82, 025106 (2011); http://dx.doi.org/10.1063/1.3553392 (7 pages) | Cited 4 times

Online Publication Date: 16 February 2011

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The design of a high pressure (HP) cell for neutron reflectivity experiments is described. The cell can be used to study solid–liquid interfaces under pressures up to 2500 bar (250 MPa). The sample interface is based on a thick silicon block with an area of about 14 cm2. This area is in contact with the sample solution which has a volume of only 6 cm3. The sample solution is separated from the pressure transmitting medium, water, by a thin flexible polymer membrane. In addition, the HP cell can be temperature-controlled by a water bath in the range 5–75°C. By using an aluminum alloy as window material, the assembled HP cell provides a neutron transmission as high as 41%. The maximum angle of incidence that can be used in reflectivity experiments is 7.5°. The large accessible pressure range and the low required volume of the sample solution make this HP cell highly suitable for studying pressure-induced structural changes of interfacial proteins, supported lipid membranes, and, in general, biomolecular systems that are available in small quantities, only. To illustrate the performance of the HP cell, we present neutron reflectivity data of a protein adsorbate under high pressure and a lipid film which undergoes several phase transitions upon pressurization.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
68.43.Mn Adsorption kinetics

An accurate continuous calibration system for high voltage current transformer

Yue Tong and Bin Hong Li

Rev. Sci. Instrum. 82, 025107 (2011); http://dx.doi.org/10.1063/1.3523341 (9 pages) | Cited 1 time

Online Publication Date: 23 February 2011

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A continuous calibration system for high voltage current transformers is presented in this paper. The sensor of this system is based on a kind of electronic instrument current transformer, which is a clamp-shape air core coil. This system uses an optical fiber transmission system for its signal transmission and power supply. Finally the digital integrator and fourth-order convolution window algorithm as error calculation methods are realized by the virtual instrument with a personal computer. It is found that this system can calibrate a high voltage current transformer while energized, which means avoiding a long calibrating period in the power system and the loss of power metering expense. At the same time, it has a wide dynamic range and frequency band, and it can achieve a high accuracy measurement in a complex electromagnetic field environment. The experimental results and the on-site operation results presented in the last part of the paper, prove that it can reach the 0.05 accuracy class and is easy to operate on site.
Show PACS
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
06.20.fb Standards and calibration

New equipment and new technique for measuring activity coefficients and Henry's constants at infinite dilution

Dominique Richon

Rev. Sci. Instrum. 82, 025108 (2011); http://dx.doi.org/10.1063/1.3553498 (8 pages) | Cited 2 times

Online Publication Date: 23 February 2011

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See Also: Erratum

Show Abstract
New equipment is presented along with various experimental procedures and setups to cover a large range of applications. It represents a considerable improvement in terms of speed, accuracy, and simplicity with respect to classical gas stripping methods known as “dilutor techniques.” Furthermore, range of conditions of its use is larger in terms of: temperatures (from 90 to 600 K), corrosive power, and toxicity of handled compounds. Solutes that could adsorb inside sampling valves or on the walls of transfer lines between sampling valve and GC detector are now studied easily; thanks to new design and procedure. Activity coefficients of one solute into one solvent at five temperatures, several repeatability tests included, are obtained in worst cases in less than 3 h. One accurate activity coefficient measurement (toluene in water) at one temperature can be realized in less than 2 min, after loading of the dilutor cell, instead of more than half an hour for unreliable results with previous equipment. It must be pointed out that the slope determination (slope of the logarithm of the exponential decay of solute composition in vapor phase which is in equilibrium with liquid phase) is the highest source of errors (flow rate, temperature, number of moles of solute are known with high accuracy with respect to slopes); they are now determined within few ‰ instead of up to tens of % in the most difficult cases leading to higher accuracies of measured activity coefficients, Henry's constants at infinite dilutions or solubility data. Successful comparisons with literature data and reproducibility tests are presented herein.
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82.80.Bg Chromatography

A small-angle scattering chamber for x-ray photon correlation spectroscopy at low temperatures

Ricardo Steinmann, Yuriy Chushkin, Chiara Caronna, Joel Chavanne, and Anders Madsen

Rev. Sci. Instrum. 82, 025109 (2011); http://dx.doi.org/10.1063/1.3553012 (6 pages)

Online Publication Date: 24 February 2011

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A low temperature sample environment for x-ray photon correlation spectroscopy measurements in small-angle scattering geometry is presented. The chamber has been designed to allow investigations of dynamical phenomena in supercooled liquids and the typical working temperature range is 110–330 K with a thermal stability ΔT/T down to 10−4. A variable external magnetic field up to 0.12 T can be applied, which is of interest in studies of, e.g., ferrofluids and liquid crystalline materials. Here, technical details about the sample environment are given together with examples of recent applications.
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78.70.Ck X-ray scattering
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
07.60.-j Optical instruments and equipment

A high-vacuum deposition system for in situ and real-time electrical characterization of organic thin-film transistors

Santiago David Quiroga, Arian Shehu, Cristiano Albonetti, Mauro Murgia, Pablo Stoliar, Francesco Borgatti, and Fabio Biscarini

Rev. Sci. Instrum. 82, 025110 (2011); http://dx.doi.org/10.1063/1.3534007 (5 pages) | Cited 1 time

Online Publication Date: 25 February 2011

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We present a home-built high-vacuum system for performing organic semiconductor thin-film growth and its electrical characterization during deposition (real-time) or after deposition (in situ). Since the environment conditions remain unchanged during the deposition and electrical characterization process, a direct correlation between growth mode and electrical properties of thin film can be obtained. Deposition rate and substrate temperature can be systematically set in the range 0.1–10 ML/min and RT-150 °C, respectively. The sample-holder configuration allows the simultaneous electrical monitoring of up to five organic thin-film transistors (OTFTs). The OTFTs parameters such as charge carrier mobility μ, threshold voltage VTH, and the on–off ratio Ion/Ioff are studied as a function of the semiconductor thickness, with a submonolayer accuracy. Design, operation, and performance of the setup are detailed. As an example, the in situ and real-time electrical characterization of pentacene TFTs is reported.
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85.30.Tv Field effect devices

Programmable smart electron emission controller for hot filament

Eli Flaxer

Rev. Sci. Instrum. 82, 025111 (2011); http://dx.doi.org/10.1063/1.3555340 (8 pages) | Cited 1 time

Online Publication Date: 25 February 2011

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In electron ionization source, electrons are produced through thermionic emission by heating a wire filament, accelerating the electrons by high voltage, and ionizing the analyzed molecules. In such a system, one important parameter is the filament emission current that determines the ionization rate; therefore, one needs to regulate this current. On the one hand, fast responses control is needed to keep the emission current constant, but on the other hand, we need to protect the filament from damage that occurs by large filaments current transients and overheating. To control our filament current and emission current, we developed a digital circuit based on a digital signal processing controller that has several modes of operation. We used a smart algorithm that has a fast response to a small signal and a slow response to a large signal. In addition, we have several protective measures that prevent the current from reaching unsafe values.
Show PACS
07.68.+m Photography, photographic instruments; xerography
79.40.+z Thermionic emission
07.05.-t Computers in experimental physics

Design, fabrication, and implementation of thermally driven outdoor testing devices for building joint sealants

C. C. White, K. T. Tan, E. P. O'Brien, D. L. Hunston, J. W. Chin, and R. S. Williams

Rev. Sci. Instrum. 82, 025112 (2011); http://dx.doi.org/10.1063/1.3543817 (9 pages) | Cited 1 time

Online Publication Date: 25 February 2011

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The paper describes the development, implementation, and testing of two thermally driven outdoor exposure instruments. These devices are unique in their ability to impose field generated thermally induced strain on sealant specimens while monitoring their resulting load and displacement. The instruments combine a fixed wood and steel supporting frame with a moving polyvinyl chloride frame, and employ differences in the coefficients of thermal expansion between the supporting frame and moving frame to induce strain on the sealant specimens. Two different kinds of instruments have been fabricated, “winter/tension” and “winter/compression” designs. In the winter/tension design, the thermally induced dimensional change is directly transferred to the specimens; while in the winter/compression design, the samples are loaded in an opposite direction with the dimensional change. Both designs are instrumented to monitor load and displacement and are built so that the strain on the specimen does not exceed ±25% over the range of temperatures expected in Gaithersburg, MD. Additionally, a weather station is colocated with the device to record environmental conditions in 1 min intervals. This combination of weather information with mechanical property data enables a direct link between environmental conditions and the corresponding sealant response. The reliability and effectiveness of these instruments are demonstrated with a typical sealant material. The results show that the instruments work according to the design criteria and provide a meaningful quantitative platform to monitor the mechanical response of sealant exposed to outdoor weathering
Show PACS
07.07.-a General equipment
07.89.+b Environmental effects on instruments (e.g., radiation and pollution effects)

Nonintrusive system for road traffic detection and characterization

M. F. Ugarte, S. Briz, and L. Durán

Rev. Sci. Instrum. 82, 025113 (2011); http://dx.doi.org/10.1063/1.3543819 (10 pages)

Online Publication Date: 28 February 2011

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Knowing the number, type, and velocity of the vehicles that drive along a road is extremely important to manage efficiently the traffic flow and also to estimate the environmental impact that the road may have in the surroundings. In this work the development and preliminary tests for a nonintrusive instrument and method for traffic characterization have been carried out. The system is part of a methodology to estimate the contaminants emitted to air due to urban and suburban road traffic. Based on a set of ultrasonic sensors, the system has shown reliability and accuracy in the determination of the number, type, and velocity of vehicles in a suburban road with several lanes and two ways. The success of this system lies on the method and data processing which overcomes the intrinsic noise problems of ultrasonic sensors. The developed system is easy to install and does not interfere with the road traffic. It is also of low cost, has no moving parts, and requires small power supply. The proposed system is an ideal tool to perform traffic studies where portability and low costs are required, for example, in environmental impact assessments studies.
Show PACS
89.20.Kk Engineering
92.60.Sz Air quality and air pollution
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