This research was funded by the Fundamental Research Funds for the Central Universities, grant number [No. NS2018017].

1. Preparation before modeling
<ol>
	<li>Obtain design point performance.
	<ol>
		<li>Open Gasturb 13. Select Variable Cycle Engine.</li>
		<li>Click on Basic Thermodynamics. Select Cycle Design. Open DemoVarCyc.CVC.</li>
		<li>Obtain the engine design point performance. These are shown on the right side of the window.</li>
	</ol>
	</li>
	<li>Obtain component maps.
	<ol>
		<li>Open Gasturb 13. Select Variable Cycle Engine.</li>
		<li>Click on Off Design. Select Standard Maps. Open DemoVarCyc.CVC.</li>
		<li>Click on Off Design Point. Then select LPC, IPC, HPC, HPT and LPT; thus, all components maps are obtained.</li>
	</ol>
	</li>
</ol>
2. Model each component of the VCE20,21,22
<ol>
	<li>Model a single component of a VCE. Take the high-pressure compressor as an example.
	<ol>
		<li>Open Matlab. Click on Simulink. Double click on Blank Model.</li>
		<li>Click on Library, and place function to model.</li>
		<li>Double click on Function. According to the working principle of the compressor, the thermodynamic equation of the compressor is described. Then describe the equation with the MATLAB function.</li>
		<li>After finishing the MATLAB function, obtain the input and output of the compressor.</li>
		<li>Use Subsystem to mask the module. Then rename it with &#8220;compressor&#8221;. Thus far, a subsystem module called &#8220;compressor&#8221; is established.</li>
	</ol>
	</li>
	<li>Use the same steps to get the subsystems of all components including inlet, fan, duct, core driven fan stage(CDFS), bypass mixer, compressor, burner, high-pressure turbine, low-pressure turbine, mixer, afterburner and nozzle.
	<ol>
		<li>Combine output of each component with input of the next component.</li>
	</ol>
	</li>
</ol>
3. Solution of the whole model
<ol>
	<li>Construct dynamic co-working equations of whole model.
	<ol>
		<li>Construct dynamic co-working equations. Construct the following 6 independent co-working equations.</li>
		<li>Determine the flow balance equation for inlet and outlet of burner: <img alt="Equation 1" src="/files/ftp_upload/59151/59151equ01.jpg" /> 
		Wa3: compressor outlet section air flow, Wf: burner fuel flow, Wg44: high-pressure turbine inlet gas flow.</li>
		<li>Determine the flow balance equation for inlet and outlet of low-pressure turbine:<img alt="Equation 2" src="/files/ftp_upload/59151/59151equ02.jpg" /> 
		Wg44: low-pressure turbine inlet section gas flow, Wg5: low-pressure turbine outlet gas flow.</li>
		<li>Determine the flow balance equation for inlet and outlet of nozzle: <img alt="Equation 3" src="/files/ftp_upload/59151/59151equ03.jpg" /> 
		Wg7: nozzle inlet gas flow, Wg9: nozzle outlet gas flow.</li>
		<li>Determine the static pressure balance equation for inlet of rear mixer: <img alt="Equation 4" src="/files/ftp_upload/59151/59151equ04.jpg" /> 
		Ps163: static pressure of main outer bypass outlet, Ps63: static pressure of inner bypass outlet.</li>
		<li>Determine the flow balance equation of fan inlet and outlet: <img alt="Equation 5" src="/files/ftp_upload/59151/59151equ05.jpg" /> 
		Wa2: fan inlet air flow, Wa21: CDFS inlet air flow, Wa13: sub-outer bypass inlet air flow</li>
		<li>Determine the flow balance equation of CDFS outlet: <img alt="Equation 6" src="/files/ftp_upload/59151/59151equ06.jpg" /> 
		Wa21: CDFS inlet air flow, Wa125: CDFS bypass inlet air flow, Wa25: compressor inlet air flow.</li>
		<li>The above 6 independent equations constitute the following equations. 
		<img alt="Equation 7" src="/files/ftp_upload/59151/59151equ07v2.jpg" /></li>
	</ol>
	</li>
	<li>Use the N-R iteration solver in TMATS to solve the above equations.
	<ol>
		<li>Before using the solver to solve the co-working equations, set the N-R iteration solver. According to the modeling process, select the following 6 initial guesses: component map auxiliaries line of fan, CDFS, high-pressure compressor, high-pressure turbine and low-pressure turbine &#946;1, &#946;2, &#946;3, &#946;4, &#946;5, sub-outer bypass inlet flow.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Bin, L., Min, C., Zhili, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Steady+Performance+Investigation+on+Various+Modes+of+an+Adaptive+Cycle+Aero-Engine+[J].">Steady Performance Investigation on Various Modes of an Adaptive Cycle Aero-Engine [J].</a> Propulsion Technology. 34 (8), 1009-1015 (2013).</li><li>Junchao, Z., Min, C., Hailong, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matching+mechanism+analysis+on+an+adaptive+cycle+engine.">Matching mechanism analysis on an adaptive cycle engine.</a> Chinese Journal of Aeronautics. (2), 22 (2017).</li><li>Lyu, Y., Tang, H., Chen, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+on+combined+variable+geometries+regulation+of+adaptive+cycle+engine+during+throttling.">A study on combined variable geometries regulation of adaptive cycle engine during throttling.</a> Applied Sciences. 6 (12), 374 (2016).</li><li>Ruffles, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aero+engines+of+the+future.">Aero engines of the future.</a> Aeronautical Journal. 107 (1072), 307-321 (2003).</li><li>Johnson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variable+cycle+engine+developments+at+General+Electric+1955-1995.">Variable cycle engine developments at General Electric 1955-1995.</a> Developments In High-Speed Vehicle Propulsion Systems. , 105-158 (1995).</li><li>French, M., Allen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NASA+VCE+test+bed+engine+aerodynamic+performance+characteristics+and+test+results.">NASA VCE test bed engine aerodynamic performance characteristics and test results.</a> , 1594 (1981).</li><li>Willis, E., Welliver, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variable-cycle+engines+for+supersonic+cruising+aircraft.">Variable-cycle engines for supersonic cruising aircraft.</a> , 759 (1976).</li><li>Allan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+Electric+Company+variable+cycle+engine+technology+demonstrator+programs.">General Electric Company variable cycle engine technology demonstrator programs.</a> , 1311 (1979).</li><li>Keith, B. D., Basu, D. K., Stevens, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aerodynamic+Test+Results+of+Controlled+Pressure+Ratio+Engine+(COPE)+Dual+Spool+Air+Turbine+Rotating+Rig.">Aerodynamic Test Results of Controlled Pressure Ratio Engine (COPE) Dual Spool Air Turbine Rotating Rig.</a> ASME Turbo Expo 2000: Power for Land, Sea, and Air. , V001T003A105-V001T003A105 (2000).</li><li>Johnson, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> US Patent. , (2005).</li><li>Vyvey, P., Bosschaerts, W., Fernandez Villace, V., Paniagua, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+an+Airbreathing+Variable+Cycle+Engine.">Study of an Airbreathing Variable Cycle Engine.</a> , 5758 (2011).</li><li>LIU, Z., WANG, Z., HUANG, H., Cai, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Numerical+simulation+on+performance+of+variable+cycle+engines.">Numerical simulation on performance of variable cycle engines.</a> Journal of Aerospace Power. 25 (6), 1310-1315 (2010).</li><li>Loftin, L. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+a+second-generation+supersonic+transport.">Toward a second-generation supersonic transport.</a> Journal of Aircraft. 11 (1), 3-9 (1974).</li><li>Mavris, D. N., Pinon, O. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Complex Systems Design &amp; Management. , 1-25 (2012).</li><li>Reed, J. A., Follen, G. J., Afjeh, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+the+aircraft+design+process+using+Web-based+modeling+and+simulation.">Improving the aircraft design process using Web-based modeling and simulation.</a> ACM Transactions on Modeling and Computer Simulation (TOMACS). 10 (1), 58-83 (2000).</li><li>Koenig, R. W., Fishbach, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GENENG:+A+Program+for+calculating+design+and+off-design+performance+for+turbojet+and+turbofan+engines.">GENENG: A Program for calculating design and off-design performance for turbojet and turbofan engines.</a> NASA Technical Note TN. D-6552. , (1972).</li><li>Sellers, J. F., Daniele, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DYNGEN:+A+program+for+calculating+steady-state+and+transient+performance+of+turbojet+and+turbofan+engines.">DYNGEN: A program for calculating steady-state and transient performance of turbojet and turbofan engines.</a> NASA Technical Note TN. D-7901. , (1975).</li><li>Reed, J., Afjeh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+interactive+graphical+propulsion+system+simulator.">Development of an interactive graphical propulsion system simulator.</a> The 30th Joint Propulsion Conference and Exhibit in Indianapolis, IN. , (1994).</li><li>Chapman, J. W., Lavelle, T. M., May, R., Litt, J. S., Guo, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Propulsion+System+Simulation+Using+the+Toolbox+for+the+Modeling+and+Analysis+of+Thermodynamic+Systems+(T+MATS).">Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T MATS).</a> , (2014).</li><li>Camporeale, S., Fortunato, B., Mastrovito, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modular+code+for+real+time+dynamic+simulation+of+gas+turbines+in+simulink.">A modular code for real time dynamic simulation of gas turbines in simulink.</a> Journal of Engineering for Gas Turbines and Power. 128 (3), 506-517 (2006).</li><li>Tsoutsanis, E., Meskin, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+performance+simulation+and+control+of+gas+turbines+used+for+hybrid+gas/wind+energy+applications.">Dynamic performance simulation and control of gas turbines used for hybrid gas/wind energy applications.</a> Applied Thermal Engineering. 147, 122-142 (2019).</li><li>Reed, J., Afjeh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+extensible+object-oriented+framework+for+distributed+computational+simulation+of+gas+turbine+propulsion+systems.">An extensible object-oriented framework for distributed computational simulation of gas turbine propulsion systems.</a> , 3565 (1998).</li><li>Muir, D. E., Saravanamuttoo, H. I., Marshall, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Health+monitoring+of+variable+geometry+gas+turbines+for+the+Canadian+Navy.">Health monitoring of variable geometry gas turbines for the Canadian Navy.</a> Journal of Engineering for Gas Turbines and Power. 111 (2), 244-250 (1989).</li></ol>

We have nothing to disclose.

Based on a graphical simulation environment, a VCE component-level model can be built rapidly through modular hierarchical architecture and object-oriented modeling technology. It offers a friendly interface to users and it is convenient to analyze and design the model19.
The main limitation of this method is the execution efficiency of the model. Because the model is written in scripting language, the model needs to be recompiled every time it runs. Thus, the execution...

Modern aircraft demands bring great challenges to the propulsion system, which need more intelligent, more efficient or even more versatile aircraft engines1. Future military propulsion systems also require both higher thrust at high speed and lower specific fuel consumption at low speed1,2,3,4. In order to meet the technical requirements of future flight missions, General Electric (GE) put forward the variable cycle engine (VCE) concept in 19555. A VCE is an aircraft engine that can perform different thermodynamic cycles by changing the geometry size or position of some components6. The Lockheed SR-71 "Blackbird" powered by a J58 turboramjet VCE has held the world record for the fastest air-breathing manned aircraft since 19767. It also proved many potential advantages of supersonic flight. In the past 50 years, GE has improved and invented several other VCEs, including a double bypass VCE8, a controlled pressure ratio engine9 and an adaptive cycle engine10. These studies involved not only the general structure and performance verification, but also the control system of the engine11. These studies have proven that the VCE can work like a high bypass ratio turbofan at subsonic flight and like a low bypass ratio turbofan, even like a turbojet at supersonic flight. Thus, the VCE can realize performance matching under different flight conditions.
When developing a VCE, a large amount of necessary verification works will be carried out. It may cost a large amount of time and outlay if all these works are performed in a physical way12. Computer simulation technology, which has already been adopted in developing a new engine, can not only reduce the cost greatly, but also avoid the potential risks13,14. Based on computer simulation technology, the development cycle of an engine will be reduced to nearly half, and the number of equipment required will be reduced dramatically15. On the other hand, simulation also plays an important role in the analysis of the engine behavior and control law development. For simulating the static design and off-design performance of engines, a program called GENENG16 was developed by the NASA Lewis Research Center in 1972. Then the research center developed DYNGEN17 derived from GENENG, and DYNGEN could simulate the transient performance of a turbojet and the turbofan engines. In 1989, NASA put forward a project, called Numerical Propulsion System Simulation (NPSS), and it encouraged researchers to construct a modular and flexible engine simulation program through the use of object-oriented programming. In 1993, John A. Reed developed the Turbofan Engine Simulation System (TESS) based on the Application Visualization System (AVS) platform through object-oriented programing18.
Meanwhile, rapid modeling based on graphical programming environment is being used gradually in simulation. The Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) package developed by NASA is based on Matlab/Simulink platform. It is open source and allows users to customize built-in component libraries. T-MATS offers a friendly interface to users and it is convenient to analyze and design the built-in JT9D model19.
In this article, the dynamic model of a type of VCE has been developed here using Simulink software. The modeling object of this protocol is a double bypass VCE. Its schematic layout is shown in Figure 1. The engine can work in both single and double bypass modes. When the Mode Select Valve (MSV) is open, the engine performs better at subsonic conditions with a relatively large bypass ratio. When the Mode Select Valve is closed, the VCE has a small bypass ratio and a better supersonic mission adaptability. To further quantize performance of the engine, a double bypass VCE model is built based on component-level modeling method.

<table>
	<tbody>
		<tr>
			<td>Gasturb</td>
			<td>GasTurb GmbH</td>
			<td>Gasturb 13</td>
			<td></td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>MathWorks</td>
			<td>R2017b</td>
			<td></td>
		</tr>
		<tr>
			<td>TMATS</td>
			<td>NASA</td>
			<td>1.2.0</td>
			<td></td>
		</tr>
	</tbody>
</table>

a rapid method for modeling a variable cycle engine

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft engines. However, developing VCE requires high costs. Thus, it is essential to build a mathematical model when developing an aircraft engine, which may avoid a large number of real tests and reduce the cost dramatically. Modeling is also crucial in control law development. In this article, based on a graphical simulation environment, a rapid method for modeling a double bypass variable cycle engine using object-oriented modeling technology and modular hierarchical architecture is described. Firstly, the mathematical model of each component is built based on the thermodynamic calculation. Then, a hierarchical engine model is built via the combination of each component mathematical model and the N-R solver module. Finally, the static and dynamic simulations are carried out in the model and the simulation results prove the effectiveness of the modeling method. The VCE model built through this method has the advantages of clear structure and real-time observation.

In order to prove the validity of the simulation model, several typical performance parameters selected in static and dynamic simulations are compared with the data in Gasturb.
In a static simulation, we compare several key performance parameters of the model with these parameters in Gasturb to verify the accuracy of the static model. Table 2 shows the result of the comparison at the design point with H=0 m, Ma=0, Wf=0.79334 kg/s under a double bypass ope...

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A Rapid Method for Modeling a Variable Cycle Engine

Here, we present a protocol to build a component-level mathematical model for a variable cycle engine.

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft ...

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7.5K Views.  Nanjing University of Aeronautics and Astronautics. Here, we present a protocol to build a component-level mathematical model for a variable cycle engine.

Video: A Rapid Method for Modeling a Variable Cycle Engine

Convergent Polishing: A Simple, Rapid, Full Aperture Polishing Process of High Quality Optical Flats &amp; Spheres

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial shape (i.e., surface figure), will converge to final surface figure with excellent surface quality under a fixed, unchanging set of polishing parameters in a single polishing iteration. In contrast, conventional full aperture polishing methods require multiple, often long, iterative cycles involving polishing, metrology and process changes to achieve the desired surface figure. The Convergent Polishing process is based on the concept of workpiece-lap height mismatch resulting in pressure differential that decreases with removal and results in the workpiece converging to the shape of the lap. The successful implementation of the Convergent Polishing process is a result of the combination of a number of technologies to remove all sources of non-uniform spatial material removal (except for workpiece-lap mismatch) for surface figure convergence and to reduce the number of rogue particles in the system for low scratch densities and low roughness. The Convergent Polishing process has been demonstrated for the fabrication of both flats and spheres of various shapes, sizes, and aspect ratios on various glass materials. The practical impact is that high quality optical components can be fabricated more rapidly, more repeatedly, with less metrology, and with less labor, resulting in lower unit costs. In this study, the Convergent Polishing protocol is specifically described for fabricating 26.5 cm square fused silica flats from a fine ground surface to a polished ~&#955;/2 surface figure after polishing 4 hr per surface on a 81 cm diameter polisher.

A novel optical polishing process, called &#8220;Convergent Polishing&#8221;, which enables faster, lower cost polishing, is described. Unlike conventional polishing processes, Convergent Polishing allows a glass workpiece to be polished in a single iteration and with high surface quality to its final surface figure without requiring changes to polishing parameters.

Convergent Polishing is a novel polishing system and method for finishing flat and spherical glass optics in which a workpiece, independent of its initial ...

A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform stress and strain rate. This can be produced by evenly loading the inner surface of a cylinder. Due to the axial symmetry, as the cylinder expands the wall is placed into a tensile hoop stress that is uniform around the circumference. While there are various techniques to generate this expansion such as explosives, electromagnetic drive, and existing gas gun techniques they are all limited in the fact that the sample cylinder must be at room temperature. We present a new method using a gas gun that facilitates experiments on cylinders from 150 K to 800 K with a consistent, repeatable loading. These highly diagnosed experiments are used to examine the effect of temperature on the fracture mechanisms responsible for failure, and their resulting influence on fragmentation statistics. The experimental geometry employs a steel ogive located inside the target cylinder, with the tip located about halfway in. A single stage light gas gun is then used to launch a polycarbonate projectile into the cylinder at 1,000 m/sec-1. The projectile impacts and flows around the rigid ogive, driving the sample cylinder from the inside. The use of a non-deforming ogive insert allows us to install temperature control hardware inside the rear of the cylinder. Liquid nitrogen (LN2) is used for cooling and a resistive high current load for heating. Multiple channels of upshifted photon Doppler velocimetry (PDV) track the expansion velocity along the cylinder enabling direct comparison to computer simulations, while High speed imaging is used to measure the strain to failure. The recovered cylinder fragments are also subject to optical and electron microscopy to ascertain the failure mechanism.

Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform ...

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.
Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of &gt; 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.
Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

The use of energy dispersive X-ray tomography in the scanning transmission electron microscope to characterize elemental distributions within single nanoparticles in three dimensions is described.

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial ...

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of stretchable electronic devices is the preparation of stretchable conductors with great mechanical stability. In this study, we developed a simple fabrication method to chemically solder the contact points between silver nanowire (AgNW) networks. AgNW nanomesh was first deposited on a glass slide via spray coating method. A reactive ink composed of silver nanoparticle (AgNPs) precursors was applied over the spray coated AgNW thin films. After heating for 40 min, AgNPs were preferentially generated over the nanowire junctions to solder the AgNW nanomesh, and reinforced the conducting network. The chemically modified AgNW thin film was then transferred to polyurethane (PU) substrates by casting method. The soldered AgNW thin films on PU exhibited no obvious change in electrical conductivity under stretching or rolling process with elongation strains up to 120%.

A simple synthesis method is used to chemically solder silver nanowire thin film to fabricate highly stretchable and conductive metal conductors.

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

A Method for Obtaining Serial Ultrathin Sections of Microorganisms in Transmission Electron Microscopy

Observing cells and cell components in three dimensions at high magnification in transmission electron microscopy requires preparing serial ultrathin sections of the specimen. Although preparing serial ultrathin sections is considered to be very difficult, it is rather easy if the proper method is used. In this paper, we show a step-by-step procedure for safely obtaining serial ultrathin sections of microorganisms. The key points of this method are: 1) to use the large part of the specimen and adjust the specimen surface and knife edge so that they are parallel to each other; 2) to cut serial sections in groups and avoid difficulty in separating sections using a pair of hair strands when retrieving a group of serial sections onto the slit grids; 3) to use a 'Section-holding loop' and avoid mixing up the order of the section groups; 4) to use a 'Water-surface-raising loop' and make sure the sections are positioned on the apex of the water and that they touch the grid first, in order to place them in the desired position on the grids; 5) to use the support film on an aluminum rack and make it easier to recover the sections on the grids and to avoid wrinkling of the support film; and 6) to use a staining tube and avoid accidentally breaking the support films with tweezers. This new method enables obtaining serial ultrathin sections without difficulty. The method makes it possible to analyze cell structures of microorganisms at high resolution in 3D, which cannot be achieved by using the automatic tape-collecting ultramicrotome method and serial block-face or focused ion beam scanning electron microscopy.

This study presents reliable and easy procedures for obtaining serial ultrathin sections of a microorganism without expensive equipment in transmission electron microscopy.

Observing cells and cell components in three dimensions at high magnification in transmission electron microscopy requires preparing serial ultrathin ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...