This work was supported in part by the Fundamental Research Funds for the Central Universities under Grant 2042022kf1059; the Nature Science Foundation of Hubei Province under Grant 2022CFB757; the China Postdoctoral Science Foundation under Grant 2022TQ0244; the Wuhan University Experiment Technology Project Funding under Grant WHU-2021-SYJS-11; the Provincial Teaching and Research Projects in Hubei Province&#39;s Colleges and Universities in 2021 under Grant 2021038; and the Provincial Laboratory Research Project in Hubei Province&#39;s Colleges and Universities under Grant HBSY2021-01.

In this work, the procedures of the microcantilever beam fracture experiment with cracks are discussed as follows, which is open for free access via&#160;http://civ.whu.rofall.net/virexp/clqd. All the&#160;steps are conducted in the online system based on the virtual simulation approach. Institutional Review Board approval was not required for this study. Consent was obtained from the student volunteers who took part in this study.
1. Accessing the system and entering the interface
<ol>
	<li>Open a web browser, and enter the URL&#160;http://civ.whu.rofall.net/virexp/clqd to access the system. 
	NOTE: The provided URL can be accessed through a mainstream web browser without a username and password.</li>
	<li>Find the virtual simulation interface using the vertical scrollbar. 
	NOTE: The virtual scene is embedded into the web.</li>
	<li>Click on the FullScreen icon at the bottom-right corner to enable a full-screen interface.</li>
	<li>Click on the Start Experiment button to start.</li>
	<li>Click on the Enter button to follow the guidance for beginners, or click on the Skip button to skip this step. 
	&#8203;NOTE: The user can choose to follow (Enter button) or skip (Skip button). The guidance for beginners provides descriptions of the entire system. The interface also highlights the operation instructions step-by-step for performing the intended operations or equipment. Figure 1 shows the equipment used in the experiment, including seven types of equipment in the mechanical and material disciplines. Beginners are recommended to follow this guidance.</li>
</ol>
2. Preparation of the materials
<ol>
	<li>Start the experiment after completing the beginner-level training. Follow the prompts on the interface to &#34;walk&#34; close to the laboratory table that contains the silicon wafers, review the differences between the normal-type and crack-type silicon wafers, and select the crack template. 
	NOTE: Enter the experiment interface, and conduct experiments according to the highlighted pathway guidance. The highlighted guidance is provided throughout the process to offer clear guidance for experimentation.</li>
	<li>Select a material from the provided materials list. 
	NOTE: The provided material list includes gold, silver, PtCuNiP, ZrTiCuNiBe, polyether-ether-ketone (PEEK), and polymethyl methacrylate (PMMA).</li>
	<li>Load the selected material onto the cutter clamp with a click on the highlighted material. Click on the highlighted ON/OFF button (on the right side) to turn on the cutter clamp, click on the Speed button (on the left side), and set the speed of the metallographic cutting machine in a pop-up interface. 
	NOTE: The user can set a proper speed as they wish. Once the speed is set by the user, the cutter clamp will be activated, and the raw bar will be cut into thin slices.</li>
	<li>Stack the mold, metal sheet, and cover sheet together in turn by clicking and dragging the highlighted object as guided in the user interface. 
	&#8203;NOTE: After cutting the material, this assembly step is necessary before nano-mold casting.</li>
</ol>
3. Molding the specimen
<ol>
	<li>Walk virtually to the high-temperature universal creep testing machine following the guidance shown in Figure 2, and virtually place the stacked specimens between the plate clamps of the universal creep testing machine. 
	NOTE: After this step, the virtual computer on the left side of the high-temperature universal creep testing machine will be highlighted.</li>
	<li>Click on the Virtual Computer, and set the test scheme on the control computer of the universal creep testing machine. 
	NOTE: After this step, the auxiliary equipment of the high-temperature universal creep testing machine for heating and vacuum pumping will be highlighted to provide guidance to the user.</li>
	<li>Click on the highlighted Heating and Vacuum Pumping Equipment, and turn on the power supply. Open the virtual mechanical pump and the backing valve in the interface by clicking on the highlighted buttons. 
	NOTE: This step completes the system vacuum control settings in the vacuum control system of the universal creep testing machine.</li>
	<li>Click on the Clear button on the Control Panel of the universal creep testing machine to clear the data. Click on the Run button on the Control Panel of the universal creep testing machine to complete the experiment, which copies the pattern on the mold to the metal sheet using the parallel plate compression molding method. 
	NOTE: After the mold casting is completed, remove the specimen, and close the backing valve and the mechanical pump, etc., of the heating and vacuum pumping equipment by clicking on the buttons in turn as required (in real heating and vacuum pumping equipment, the reverse order may cause the molecular pump to burn out).</li>
	<li>Click on the Virtual Computer again, and check the experimental data on the control computer of the universal creep testing machine.</li>
	<li>Open the cover plate on the metallographic specimen inlaying machine, and place the specimen.
	<ol>
		<li>Click on the highlighted PMMA powder to pour the prepared powder, and click on the highlighted mold to place it on top of the PMMA powder.</li>
		<li>Click on the highlighted hand wheel to adjust the position of the mold, which will cover the cover plate automatically. Click on the ON/OFF button to turn on the inlaying machine. Take out the PMMA inlaid specimen after cooling. 
		NOTE: The molded specimen should be mounted on the inlaying machine in the correct direction, as shown in Figure 3, in which the thermoplastic material PMMA is used in the experiment. Make sure the PMMA powder melts and adheres to the surface of the specimen. The bottom-left corner of Figure 4 illustrates the correct direction after the user confirms the selection shown in Figure 3.</li>
	</ol>
	</li>
	<li>Enter the room for polishing and corrosion following the pathway guidance, as shown in Figure 5. Find the highlighted polishing machine, and click on the gripper of the polishing machine to mount the inlaid specimen to the gripper. Set the speed to grind and polish the specimen to remove the molded material substrate. 
	&#8203;NOTE: Grind the mold on one side of the mold until the pattern on the mold is exposed.</li>
</ol>
4. Specimen characterization
<ol>
	<li>Register in the e-notebook before using a chemical. Open the chemical storage cabinet, and take out the solid KOH and acetone solution. Click on the highlighted beaker to use the acetone solution to clean the specimen. Click on another highlighted beaker and solid KOH for corrosion liquid preparation to prepare a 10% KOH solution. Click on the highlighted KOH solution and the specimen to corrode the specimen into a metallographic specimen. 
	NOTE: In this experiment, to remove the silicon mold, a 6 mol/L KOH solution is usually prepared, the specimen is placed in the preparation solution, and the beaker containing the corrosion solution and the specimen is placed on a hot plate to heat up to accelerate the corrosion rate.</li>
	<li>Clean the specimen after removing the silicon substrate, and run a characterized testing with the prepared specimen under an optical microscope. 
	&#8203;NOTE: Remember to determine the integrity of the specimen after the grinding and corrosion.</li>
</ol>
5. Specimen loading and nanoindenter installation
<ol>
	<li>Load the specimen onto the sample stage of the nanoindenter. Choose the cone indenter to mount it on the driver of the micro- and nanomechanics testing system. Click on the highlighted drive to connect it with the nanoindenter. 
	&#8203;NOTE: The &#34;Pin&#34; must be inserted into the drive shaft when installing the indenter, and since the drive shaft is a slender bar, the latch avoids damaging the drive shaft when screwing the indenter with a threaded end into the drive.</li>
</ol>
6. SEM in situ experiment
<ol>
	<li>Click the Vent button in the SEM control software after installing the indenter of the nanoindenter and loading the specimen as described in 5.1.</li>
	<li>Open the SEM chamber after breaking the vacuum, install the nanoindenter on the SEM sample stage, and connect the wires (Figure 6 shows an example of connecting one of the wires).</li>
	<li>Open the control software of the nanoindenter, and select Loaded Indenter Range &#62; Select Experimental Protocol &#62; Start Controller &#62; Init* (Sample Stage Initialization). 
	NOTE: The position initialization process of the nanoindenter sample stage must be carried out in the state in which the SEM cavity is open to avoid the initialization process of the nanoindenter sample stage hitting the pole of the SEM electron outlet port.</li>
	<li>Close the SEM chamber, and click on the Pump button on the SEM control software.</li>
	<li>Click on the Up or Down button in the SEM control software to adjust the position of the sample stage so that the sample to be measured falls into the SEM field of view. Click on the OK button to fix the position. Click on the highlighted EHT button to turn on the electron gun. Click on the Camera button, and switch to the electron microscopy observation mode. 
	NOTE: The indenter of the nanoindenter should be controlled in observation mode to gradually approach the sample to be measured.</li>
	<li>Click on the Run button on the control software of the nanoindenter. 
	NOTE: During the experiment, it is necessary to observe and record the deformation characteristics and failure process during the loading process of the specimen and to open the original data of the experiment in the data analysis window after the experiment is complete for plotting and exporting the data.</li>
	<li>Click the Stop button on the control software of the nanoindenter to terminate the experiment. 
	NOTE: The virtual simulation experiment ends here. The user is asked to complete the online exam exercise in the virtual interface after the experimentation.</li>
</ol>

<ol>
	<li>Chong, K., Chuang, T. J., Anderson, P. M., Wu, M. K., Hsieh, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano+mechanics/materials+research.">Nano mechanics/materials research.</a> Nanomechanics of Materials and Structures. , 13-22 (2006).</li><li>Ratner, B. M., Ratner, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nanotechnology: A Gentle Introduction to the Next Big Idea. , (2003).</li><li>Li, Y., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precipitation+behavior+in+boundaries+and+its+influence+on+impact+toughness+in+22Cr25Ni3W3CuCoNbN+steel+during+short-term+ageing.">Precipitation behavior in boundaries and its influence on impact toughness in 22Cr25Ni3W3CuCoNbN steel during short-term ageing.</a> Materials Science and Engineering A. 809, 140924 (2021).</li><li>Li, Y., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strengthening+mechanisms+and+creep+rupture+behavior+of+advanced+austenitic+heat+resistant+steel+SA-213+S31035+for+A-USC+power+plants.">Strengthening mechanisms and creep rupture behavior of advanced austenitic heat resistant steel SA-213 S31035 for A-USC power plants.</a> Materials Science and Engineering A. 775, 138991 (2020).</li><li>Wang, X., Li, Y., Chen, D., Sun, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precipitate+evolution+during+the+aging+of+Super304H+steel+and+its+influence+on+impact+toughness.">Precipitate evolution during the aging of Super304H steel and its influence on impact toughness.</a> Materials Science and Engineering A. 754, 238-245 (2019).</li><li>Juri, A. Z., Basak, A. K., Yin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-situ+SEM+cyclic+nanoindentation+of+pre-sintered+and+sintered+zirconia+materials.">In-situ SEM cyclic nanoindentation of pre-sintered and sintered zirconia materials.</a> Journal of the Mechanical Behavior of Biomedical Materials. 126, 105068 (2022).</li><li>Nautiyal, P., Boesl, B., Agarwal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+during+in-situ+mechanical+testing:+Some+practical+considerations+and+limitations.">Challenges during in-situ mechanical testing: Some practical considerations and limitations.</a> In-situ Mechanics of Materials. , 227-238 (2020).</li><li>Nautiyal, P., Zhang, C., Loganathan, A., Boesl, B., Agarwal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-temperature+mechanics+of+boron+nitride+nanotube+&amp;#34;Buckypaper&amp;#34;+for+engineering+advanced+structural+materials.">High-temperature mechanics of boron nitride nanotube &amp;#34;Buckypaper&amp;#34; for engineering advanced structural materials.</a> ACS Applied Nano Materials. 2 (7), 4402-4416 (2019).</li><li>Cao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlations+between+microstructure,+fracture+morphology,+and+fracture+toughness+of+nanocrystalline+Ni-W+alloys.">Correlations between microstructure, fracture morphology, and fracture toughness of nanocrystalline Ni-W alloys.</a> Scripta Materialia. 113, 84-88 (2016).</li><li>Lei, Z., et al. <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+web-based+digital+twin+thermal+power.">Toward a web-based digital twin thermal power.</a> IEEE Transactions on Industrial Informatics. 18 (3), 1716-1725 (2022).</li><li>Lei, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+virtual+simulation+to+digital+twins+in+online+laboratories.">From virtual simulation to digital twins in online laboratories.</a> 2021 40th Chinese Control Conference. , 8715-8720 (2021).</li><li>Dede, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immersive+interfaces+for+engagement+and+learning.">Immersive interfaces for engagement and learning.</a> Science. 323 (5910), 66-69 (2009).</li><li>Sun, X., Liu, H., Wu, G., Zhou, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Training+effectiveness+evaluation+of+helicopter+emergency+relief+based+on+virtual+simulation.">Training effectiveness evaluation of helicopter emergency relief based on virtual simulation.</a> Chinese Journal of Aeronautics. 31 (10), 2000-2012 (2018).</li><li>Lei, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactive+and+visualized+online+experimentation+system+for+engineering+education+and+research.">Interactive and visualized online experimentation system for engineering education and research.</a> Journal of Visualized Experiments. (177), e63342 (2021).</li><li>Gal&#225;n, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safe+experimentation+in+optical+levitation+of+charged+droplets+using+remote+labs.">Safe experimentation in optical levitation of charged droplets using remote labs.</a> Journal of Visualized Experiments. (143), e58699 (2019).</li><li>Ouyang, S. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Unity3D-based+interactive+three-dimensional+virtual+practice+platform+for+chemical+engineering.">A Unity3D-based interactive three-dimensional virtual practice platform for chemical engineering.</a> Computer Applications in Engineering Education. 26 (1), 91-100 (2018).</li></ol>

The authors have nothing to disclose.

One of the advantages of virtual simulation experiments is that they allow users to conduct the experiments without concerns regarding damaging the physical system or causing any harm to themselves11. Thus, users can conduct any operations, including either correct or wrong operations. However, the system gives the user a warning message that is integrated into the interactive experiment to guide them to conduct the experiments correctly when a wrong operation is conducted. In this way, users can ...

Mechanics is one of the basic disciplines in engineering, as shown by the emphasis placed on the foundation of mathematical mechanics and theoretical knowledge and the attention given to the cultivation of students&#39; practical abilities. With the rapid advancement of modern science and technology, nanoscience and technology have had a huge impact on human life and the economy. Rita Colwell, the former director of the US National Science Foundation (NSF), declared in 2002 that nanoscale technology would have an impact equal to the Industrial Revolution1 and noted that nanotechnology is truly a portal to a new world2. The mechanical properties of materials at the nanoscale are one of the most fundamental and necessary factors for the development of high-tech applications, such as nano-devices3,4,5. The mechanical behavior of materials at the nanoscale and the structural evolution under stress have become important issues in current nanomechanical research.
In recent years, the development and improvement of nanoindentation technology, electron microscopy technology, scanning probe microscopy, etc., have made &#34;in situ mechanics&#34; experiments an advanced testing technique important in nanomechanics research6,7. Obviously, from the perspective of teaching and scientific research, it is necessary to introduce frontier experimental techniques into the traditional teaching content regarding mechanical experiments.
However, experiments of microscopic mechanics are significantly different from macroscopic basic mechanics experiments. On the one hand, although the relevant instruments and equipment have been popularized in almost all colleges and universities, their number is limited because of the high price and maintenance cost. In the short term, it is impossible to purchase enough equipment for offline teaching. Even if there are financial resources, the management and maintenance costs of offline experiments are too high, since this type of equipment has high-precision characteristics.
On the other hand, in situ mechanics experiments such as scanning electron microscopy (SEM) are very comprehensive, with high operational requirements and an extremely long experimental period8,9. Offline experiments require students to be highly focused for a long time, and misoperation can damage the instrument. Even with very skilled individuals, a successful experiment requires a few days to complete, from preparing qualified specimens to loading the specimens for in situ mechanics experiments. Therefore, the efficiency of offline experimental teaching is extremely low.
To address the above issues, virtual simulation can be utilized. The development of virtual simulation experiment teaching can address the cost and quantity bottleneck of in situ mechanics experimental equipment and, thus, allow students to easily use various advanced pieces of equipment without damaging high-tech instruments. Simulation experiment teaching also enables students to access the virtual simulation experiment platform via the internet anytime and anywhere. Even for some low-cost instruments, students can use virtual instruments in advance for training and practice, which may improve teaching efficiency.
Considering the accessibility and availability of web-based systems10, in this work, we present a web-based virtual simulation experimentation system that can provide a set of experiments related to fundamental operations in mechanics and materials, with a focus on the in situ mechanics experiment.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Virtual interface</td>
			<td>None</td>
			<td>None</td>
			<td>http://civ.whu.rofall.net/virexp/clqd</td>
		</tr>
	</tbody>
</table>

a virtual simulation experiment of mechanics: material deformation and failure based on scanning electron microscopy

This work presents a set of comprehensive virtual experiments to detect material deformation and failure. The most commonly used pieces of equipment in mechanics and material disciplines, such as a metallographic cutting machine and a high-temperature universal creep testing machine, are integrated into a web-based system to provide different experimental services to users in an immersive and interactive learning environment. The protocol in this work is divided into five subsections, namely, the preparation of the materials, molding the specimen, specimen characterization, specimen loading, nanoindenter installation, and SEM in situ experiments, and this protocol aims to provide an opportunity for users regarding the recognition of different equipment and the corresponding operations, as well as the enhancement of laboratory awareness, etc., using a virtual simulation approach. To provide clear guidance for the experiment, the system highlights the equipment/specimen to be used in the next step and marks the pathway that leads to the equipment with a conspicuous arrow. To mimic the hands-on experiment as closely as possible, we designed and developed a three-dimensional laboratory room, equipment, operations, and experimental procedures. Moreover, the virtual system also considers interactive exercises and registration before using chemicals during the experiment. Incorrect operations are also allowed, resulting in a warning message informing the user. The system can provide interactive and visualized experiments to users at different levels.

The system provides clear guidance for the user&#39;s operations. First, beginner-level training is integrated when a user enters the system. Second, the equipment and the laboratory room to be used for the next-step operation are highlighted.
The system can be used for several different educational purposes for different levels of students. For example, Figure 1 includes seven of the most commonly used types of equipment in the mechanical and mat...

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A Virtual Simulation Experiment of Mechanics: Material Deformation and Failure Based on Scanning Electron Microscopy

This work presents a three-dimensional virtual simulation experiment for material deformation and failure that provides visualized experimental processes. Through a set of experiments, users can become familiar with the equipment and learn the operations in an immersive and interactive learning environment.

This work presents a set of comprehensive virtual experiments to detect material deformation and failure. The most commonly used pieces of equipment in ...

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Unit 1

Elasticity, Creep, and Shrinkage in Concrete

SCIENTISTS IN ACTION

2.0K vues.  Wuhan University. Le système peut être utilisé pour enseigner à nos étudiants les protocoles expérimentaux, l’utilisation de l’équipement et la vérification théorique, leur permettant d’améliorer à plusieurs reprises leurs opérations et leurs compétences en laboratoire. Un côté des expériences de simulation virtuelle tridimensionnelle peut être mené pour détecter la déformation du matériau et la défaillance sans craindre de nuire au système physique ou de se blesser. Après avoir a...

Vidéo: A Virtual Simulation Experiment of Mechanics: Material Deformation and Failure Based on Scanning Electron Microscopy

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

In Depth Analyses of LEDs by a Combination of X-ray Computed Tomography (CT) and Light Microscopy (LM) Correlated with Scanning Electron Microscopy (SEM)

In failure analysis, device characterization and reverse engineering of light emitting diodes (LEDs), and similar electronic components of micro-characterization, plays an important role. Commonly, different techniques like X-ray computed tomography (CT), light microscopy (LM) and scanning electron microscopy (SEM) are used separately. Similarly, the results have to be treated for each technique independently. Here a comprehensive study is shown which demonstrates the potentials leveraged by linking CT, LM and SEM. In depth characterization is performed on a white emitting LED, which can be operated throughout all characterization steps. Major advantages are: planned preparation of defined cross sections, correlation of optical properties to structural and compositional information, as well as reliable identification of different functional regions. This results from the breadth of information available from identical regions of interest (ROIs): polarization contrast, bright and dark-field LM images, as well as optical images of the LED cross section in operation. This is supplemented by SEM imaging techniques and micro-analysis using energy dispersive X-ray spectroscopy.

In Depth Analyses of LEDs by a Combination of X-ray Computed Tomography CT and Light Microscopy LM Correlated with Scanning Electron Microscopy SEM

A workflow for comprehensive micro-characterization of active optical devices is outlined. It contains structural as well as functional investigations by means of CT, LM and SEM. The method is demonstrated for a white LED which can be still be operated during characterization.

In failure analysis, device characterization and reverse engineering of light emitting diodes (LEDs), and similar electronic components of ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits &#34;hand controlled manipulation&#34; (HCM), in which the SPM tip is moved according to the motion of the experimenter&#39;s hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

We demonstrate the precise manipulation of individual organic molecules on a metal surface with the tip of a scanning probe microscope driven in 3D by the experimenter's hand using a motion capture system and fully immersive virtual reality goggles.

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

Study of Siphon Breaker Experiment and Simulation for a Research Reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively.
To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli&#39;s equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system.
In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results well.

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent ...

Single-Digit Nanometer Electron-Beam Lithography with an Aberration-Corrected Scanning Transmission Electron Microscope

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by employing an aberration-corrected scanning transmission electron microscope as the exposure tool. Here, we present results of single-digit nanometer patterning of two widely used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. The method achieves sub-5 nanometer features in poly (methyl methacrylate) and sub-10 nanometer resolution in hydrogen silsesquioxane. High-fidelity transfer of these patterns into target materials of choice can be performed using metal lift-off, plasma etch, and resist infiltration with organometallics.

We use an aberration-corrected scanning transmission electron microscope to define single-digit nanometer patterns in two widely-used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. Resist patterns can be replicated in target materials of choice with single-digit nanometer fidelity using liftoff, plasma etching, and resist infiltration by organometallics.

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by ...