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In the Publish! series, we’re showcasing a piece of work which is one of the University of Stuttgart’s most-cited publications this year. The topic is the use of metal hydrides as an energy store for hydrogen and as a chemically active substance in batteries.

Using hydrogen as an energy source

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Hydrogen, which does not emit CO2 into the atmosphere when it is used, is of huge significance as an energy source. It can be used for a variety of different purposes and can also be used as an energy store. As a doctoral researcher at the Institute of Material Science at the University of Stuttgart, Efi Hadjixenophontos worked together with other doctoral students on the Ecostore project run by the Marie Skłodowska-Curie Actions (MSCA) research fellowship program to carry out research into how hydrogen can be used as an energy store and in solid-state batteries. The group published its findings in MDPI Open Access Journals in March 2020. The paper has been one of the University of Stuttgart’s most-cited publications this year.

Original publication

Hadjixenophontos, Efi; Dematteis, Erika Michela; Berti, Nicola; Wolczyk, Anna Roza; Huen, Priscilla; Brighi, Matteo; Le, Thi Thu; Santoru, Antonio; Payandeh, Seyed Hosein; Peru, Filippo; Dao, Anh Ha; Liu, Yinzhe; Heere, Michael. (2020) A Review of the MSCA ITN ECOSTORE-Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity. In: MDPI Open Access Journals,

Space-saving and safe

Hydrogen has a lower volume if it is used in a solid state in metal hydride instead of as a gas. When used in energy stores or batteries, metal hydrides take up about a third less space than hydrogen in gaseous form. Hydrogen in a solid state is also easier to handle than in gaseous form, which is highly explosive.

Which are the most suitable materials?

“One of the most promising materials which is considered a pure metal hydride is magnesium hydride (MgH2)”, explains Dr. Efi Hadjixenophontos. In order to produce a thin layer of the material in nanoscale, metal is bombarded with ions in a so-called ion-beam sputter chamber so that metal ions are released which form a thin layer of magnesium hydride. This is the most suitable form of the material for investigating the fundamental behaviour of hydrogen motion. With the help of specially developed hydrogen reactors and microscopy techniques conducted at the Institute of Material Science, Hadjixenophontos was able to evaluate the diffusion over a wide range of temperatures. Furthermore, the researchers synthesized other hybrid materials such as amides, imides, boron hydrides and rare-earth metal hydrides.

New insights into the processes observed in batteries

Batteries which use magnesium hydride belong to the family of so-called conversion reaction batteries. In conventional Li-ion batteries, the lithium ions move to and fro between the negative and positive electrodes when charging and discharging without a chemical reaction taking place. “In the conversion batteries which we looked into though, a chemical reaction does happen. When the batteries are being charged, the magnesium hydride reacts with the lithium hydride. This reaction unfortunately isn’t always reversible though, which poses a challenge in terms of the lifespan of the battery”, is how the researcher describes the processes observed in the new types of battery.

Batteries can be produced without lithium

If metal hydrides such as magnesium hydride are used in batteries, it is also possible to use batteries which aren’t based on lithium but instead for example with sodium, as is discussed in the published work. This is a big advantage, because lithium is extremely rare.

Larger capacity

Batteries with metal hydride have a larger capacity than conventional batteries. “This means a longer range if they are used in vehicles in the future”, says Dr Hadjixenophontos talking about the advantages they offer, “because the batteries take up less space and are lighter despite the higher capacity, this means that it will also become viable to use them for emergency power generators or other mobile devices.”

Creating a network

As well as carrying out research, also on the agenda for the Marie Skłodowska-Curie Actions fellowship program is creating a network. A total of nine doctoral students and two postdocs from different universities, companies and scientific institutions from Germany and abroad were involved in the Ecostore project. Reciprocal research stays for participants were also integrated into the project. This meant that Efi Hadjixenophontos was able to spend two months as a guest researcher at both Tohoku University in Japan and at the French National Centre for Scientific Research (CNRS) in Paris. In addition, she visited the French subsidiary of the company SAFT Batteries. Dr. Efi Hadjixenophontos completed her doctorate at the Institute of Material Science at the University of Stuttgart under Prof. Guido Schmitz. “I’m very thankful for the fantastic research environment at the institute and for the commitment shown by Prof. Schmitz”, she points out. Since 2019 she has been working as a materials scientist at the Institute of Engineering Thermodynamics at the German Aerospace Center (DLR).

Source: University of Stuttgart

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Linux 101: Renaming files and folders

In your quest to migrate to the Linux operating system, you’ve found the command line interface a must-know skill. Fortunately, Jack Wallen is here to help you with the basics.

I’m going to help you learn a bit more about Linux. If you’re new to the operating system, there are quite a few fundamental tasks you’re going to need to know how to do. One such task is renaming files and folders. 

You might think there’s a handy rename command built into the system. There is, but it’s not what you assume. Instead of renaming a file or folder, you move it from one name to another, with the mv command. This task couldn’t be any easier. 

SEE: Linux: The 7 best distributions for new users (free PDF) (TechRepublic)

For instance, if you have a file named and you want to rename it For that you’d issue the command: 


The first file name is the original and the second is the new name–simple. For folders, it’s the same thing. If you have a folder named “project” and you want to rename it “python_projects.” For that, you’d issue the command: 

mv projects python_projects

One nice thing about the mv command (besides its simplicity) is that it does retain the original directory attributes, so you don’t have to worry about reassigning things like permissions and ownership. Even if you issue the command with sudo privileges, it won’t shift the directory ownership to root. 

Another handy feature is that you don’t have to leave the file in the same directory. If you have in your home directory and you want to rename it to “” and move it to /usr/local/bin/ at the same time. Once again, that’s as simple as:

 sudo mv /usr/local/bin/

The reason why you have to use sudo is because the /usr/local/bin directory is owned by root, so your standard user won’t have permission to move the file into the directory. 

And that’s all there is to renaming files and folders from the Linux command line. Enjoy that new skill.

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Improving Makeup Face Verification by Exploring Part-Based Representations

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Facial recognition has been more and more widely used recently; however, there are some issues in this field. One of them is facial makeup because it can change the facial appearance and compromise a biometric system. A recent study suggests a technique to improve facial recognition with makeup.

Improving Makeup Face Verification by Exploring Part Based Representations

Image credit: kaboompics via Pixabay, free licence

It explores part-based representations. Different parts of a face are affected by cosmetics differently; therefore, this approach can increase the accuracy of face recognition. Two strategies of cropping the face are analyzed.

Firstly, splitting into four components: left periocular, including the eye and eyebrow, right periocular, nose, and mouth. Secondly, dividing the face into three facial thirds. After cropping, features are extracted using convolutional neural networks (CNN) and fused with the holistic score. The results show that this approach let to achieve improvements even without fine-tuning or retraining CNN models.

Recently, we have seen an increase in the global facial recognition market size. Despite significant advances in face recognition technology with the adoption of convolutional neural networks, there are still open challenges, as when there is makeup in the face. To address this challenge, we propose and evaluate the adoption of facial parts to fuse with current holistic representations. We propose two strategies of facial parts: one with four regions (left periocular, right periocular, nose and mouth) and another with three facial thirds (upper, middle and lower). Experimental results obtained in four public makeup face datasets and in a challenging cross-dataset protocol show that the fusion of deep features extracted of facial parts with holistic representation increases the accuracy of face verification systems and decreases the error rates, even without any retraining of the CNN models. Our proposed pipeline achieved state-of-the-art performance for the YMU dataset and competitive results for other three datasets (EMFD, FAM and M501).

Research paper: de Assis Angeloni, M. and Pedrini, H., “Improving Makeup Face Verification by Exploring Part-Based Representations”, arXiv:2101.07338. Link:

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Nokia 1.4, Nokia 6.3, and Nokia 7.3 May Launch in Late Q1 or Early Q2 This Year

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Nokia 1.4, Nokia 6.3, and Nokia 7.3 could launch in Q1 or early Q2 of this year, a new report claims. All three of these Nokia phones have been in the news in the past with speculations around their release. While Nokia 1.4 is relatively new, Nokia 6.3 and Nokia 7.3 were originally expected to launch in the third quarter of 2020. It is also possible that whenever these two Nokia phones launch, they could also be named Nokia 6.4 or Nokia 7.4.

Starting with Nokia 1.4, the phone has made its way through multiple listings, as per a report by Nokiapoweruser. The report states that the phone may launch in February. Recently, specifications and pricing for Nokia 1.4 were tipped, suggesting a 6.51-inch HD+ LCD display, a quad core processor, 1GB + 16GB storage configuration, and dual-rear camera setup. The phone is expected to be priced under EUR 100 (roughly Rs. 8,800).

Nokia 6.3 and Nokia 7.3, on the other hand, have been in the news for quite a while now. The report by Nokiapoweruser states that they may launch late in the first quarter or early in the second quarter of 2021. These phones could also launch as Nokia 6.4 and Nokia 7.4.

Nokia 6.3 has been tipped in the past to come with the Qualcomm Snapdragon 730 SoC and a 24-megapixel shooter. Nokia 7.3 may feature a 6.5-inch full HD+ display with a hole-punch cutout and be powered by the Qualcomm Snapdragon 690 SoC. It could come with a 48-megapixel primary sensor and a 24-megapixel selfie shooter. Nokia 6.3 and Nokia 7.3 are expected to be backed by a 4,500mAh and a 5,000mAh battery, respectively.

Originally, the two phones were expected to launch at IFA 2020 in September. Then, it was reported that they may launch in November. Even now, Nokia or brand licensee HMD Global has not shared any information on the launch date for these phones.

Is Android One holding back Nokia smartphones in India? We discussed this on Orbital, our weekly technology podcast, which you can subscribe to via Apple Podcasts, Google Podcasts, or RSS, download the episode, or just hit the play button below.


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