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Hydrogen storage within a metal hydride involves exothermic and endothermic processes for hydrogen absorption and desorption, respectively. In addition, the thermal conductivity of the particulate metal hydride (i.e., powder) after repeated absorption processes is extremely low compared to its bulk phase. Low heat conduction through the metal hydride powder makes the hydrogen charging slow; thus, appropriate thermal management is necessary to achieve the fast charging time with the maximum energy density. In this work, we propose a thermal design of a portable hydrogen storage system made of a 300-mL vessel by balancing the internal and external thermal resistances. A copper-mesh structure is employed inside the vessel for enhancing the effective thermal conductivity of metal hydride powder (i.e., reducing the internal thermal resistance). On the other hand, a compact fan is used for enhancing the forced convection heat transfer from the vessel (i.e., reducing the external thermal resistance). Consequently, a copper-mesh structure sacrificing 4.3% of the internal vessel volume was manufactured by following the thermal design. In addition, the effect of the proposed thermal design was confirmed by actual hydrogen-charging experiments that showed 73.5% reduction of the charging time.

© 2022 NATO CCDCOE.Network Intrusion Detection Systems (IDSs) have been used to increase the level of network security for many years. The main purpose of such systems is to detect and block malicious activity in the network traffic. Researchers have been improving the performance of IDS technology for decades by applying various machine-learning techniques. From the perspective of academia, obtaining a quality dataset (i.e. a sufficient amount of captured network packets that contain both malicious and normal traffic) to support machine learning approaches has always been a challenge. There are many datasets publicly available for research purposes, including NSL-KDD, KDDCUP 99, CICIDS 2017 and UNSWNB15. However, these datasets are becoming obsolete over time and may no longer be adequate or valid to model and validate IDSs against state-of-the-art attack techniques. As attack techniques are continuously evolving, datasets used to develop and test IDSs also need to be kept up to date. Proven performance of an IDS tested on old attack patterns does not necessarily mean it will perform well against new patterns. Moreover, existing datasets may lack certain data fields or attributes necessary to analyse some of the new attack techniques. In this paper, we argue that academia needs up-to-date high-quality datasets. We compare publicly available datasets and suggest a way to provide up-to-date high-quality datasets for researchers and the security industry. The proposed solution is to utilize the network traffic captured from the Locked Shields exercise, one of the world's largest live-fire international cyber defence exercises held annually by the NATO CCDCOE. During this three-day exercise, red team members consisting of dozens of white hackers selected by the governments of over 20 participating countries attempt to infiltrate the networks of over 20 blue teams, who are tasked to defend a fictional country called Berylia. After the exercise, network packets captured from each blue team's network are handed over to each team. However, the countries are not willing to disclose the packet capture (PCAP) files to the public since these files contain specific information that could reveal how a particular nation might react to certain types of cyberattacks. To overcome this problem, we propose to create a dedicated virtual team, capture all the traffic from this team's network, and disclose it to the public so that academia can use it for unclassified research and studies. In this way, the organizers of Locked Shields can effectively contribute to the advancement of future artificial intelligence (AI) enabled security solutions by providing annual datasets of up-to-date attack patterns.

A novel concept for diesel fuel processing utilizing H2O2 is suggested to obtain the high-purity H2 required for air-independent propulsion using polymer electrolyte membrane fuel cells for use in submarines and unmanned underwater vehicles. The core components include 1) a diesel-H2O2 autothermal reforming (ATR) reactor to produce H2-rich gas, 2) a water-gas shift (WGS) reactor to convert CO to H2, and 3) a H2 separation membrane to separate only high-purity H2. Diesel and H2O2 can easily be pressurized as they are liquids. The application of the H2 separation membrane without a compressor in the middle of the process is thus advantageous. In this paper, the characteristics of pressurized ATR and WGS reactions are investigated according to the operating conditions. In both reactors, the methanation reaction is enhanced as the pressure increases. Then, permeation experiments with a H2 separation membrane are performed while varying the temperature, pressure difference, and inlet gas composition. In particular, approximately 90% of the H2 is recovered when the steam-separated rear gas of the WGS reactor is used in the H2 separation membrane. Finally, based on the experimental results, design points are suggested for maximizing the efficiency of the diesel-H2O2 fuel processor.

To investigate the feasibility of scaling up bio-inspired organic materials as cathode materials in lithium ion batteries, large-sized pouch cells are successfully prepared via tape casting using lumichrome with an alloxazine structure and aqueous styrene butadiene rubber-carboxymethyl cellulose (SBR-CMC) binders. A battery module with a two-in-series, six-in-parallel (2S6P) configuration is also successfully fabricated and is able to power blue LEDs (850 mW). Lumichrome shows no structural changes during the fabrication processes used to produce the positive electrode. The large-sized pouch cells show two sets of cathodic and anodic peaks with average potentials of 2.58 V and 2.26 V vs. Li/Li + , respectively. The initial discharge capacities are 142 mAh g −1 and 148 mAh g −1 for ethylene carbonate-dimethyl carbonate (EC-DMC) and tetraethylene glycol dimethyl ether (TEGDME) electrolytes, respectively, similar to that of a coin cell (149 mAh g −1 ). The EC-DMC-injected pouch cells exhibit higher rate performance and cyclability than the TEGDME-injected ones. The TEGDME electrolyte is not suitable for lithium metal anodes because of electrolyte decomposition and subsequent cell swelling.

This paper presents a polymer electrolyte membrane (PEM) fuel cell stack that is specifically designed for the propulsion of an underwater vehicle (UV). The stack for a UV must be continuously operated in a closed space using hydrogen and pure oxygen; it should meet various performance requirements such as high hydrogen and oxygen utilizations, low hydrogen and oxygen consumptions, a high ramp-up rate, and a long lifetime. To this end, a cascade-type stack design is employed and the cell components, including the membrane electrode assembly and bipolar plate, are evaluated using long-term performance tests. The feasibility of a fabricated 4-kW-class stack was confirmed through various performance evaluations. The proposed cascade-type stack exhibited a high efficiency of 65% and high hydrogen and oxygen utilizations of 99.89% and 99.68%, respectively, resulting in significantly lesser purge-gas emissions to the outside of the stack. The load-following test was successfully performed at a high ramp-up rate. The lifetime of the stack was confirmed by a 3500-h performance test, from which the degradation rate of the cell voltage was obtained. The advantages of the cascade-type stack were also confirmed by comparing its performance with that of a single-stage stack operating in dead-end mode.

A hydrogen energy storage system for portable/mobile applications such as personal power sources and unmanned underwater vehicles is developed. An application-oriented design and system integration strategy are newly suggested to maximize energy density while incorporating conventional technologies for the electrolyzer (Ely), the metal hydride (MH), and the polymer electrolyte membrane fuel cell (PEMFC). To improve both the energy density and usability, the systems for charging and discharging are separated. The charging component is composed of a water Ely (0.5 Nm3 h−1) and an MH cooling device as one system. The discharging component consists of an MH (900 NL H2), a PEMFC stack (50 W), and a power conditioning system (PCS) as a single system. The MH material and engineering properties are investigated to find an MH that is suitable for the target system. The hybrid design and operating strategy of the PEMFC and PCS are developed to maximize energy density. The prototype system provides a nominal power output of 31.5 W at 12 V for 38 h with one recharging. We find it significant that the discharging component shows an energy density of 410 Wh L−1, which is twice that of conventional energy storage systems at the 2.9-L level.

A diesel reformer start-up strategy using hydrogen peroxide (H2O2) decomposition heat is first proposed for subsea applications such as submarines and unmanned underwater vehicles (UUVs), requiring no oxygen. H2O2 can supply not only both the oxygen and steam required for the diesel autothermal reforming (ATR) reaction but also heat via the catalytic H2O2 decomposition reaction. We utilize the high-quality heat from H2O2 for the reformer start-up by evaporating and chemically decomposing the 50 wt% concentration H2O2. A comparative reformer start-up strategy study is performed between conventional diesel ATR and diesel-H2O2 ATR using a 1 kWe-class diesel reformer. For the conventional start-up, three steps of partial oxidation, partial load ATR, and full load ATR are required to heat the ATR reformer after electrically preheating the ATR catalyst. However, the proposed strategy requires only one full load ATR step after preheating the ATR catalyst using H2O2 decomposition heat. With the suggested start-up strategy, a simplified sequence with negligible temperature fluctuations and a 57% start-up time reduction are achieved. We find it significant that the full load flowrate of superheated steam generation from the H2O2 decomposer is a critical factor in simplifying and shortening the start-up procedure.

Thermal batteries are primary power sources for military applications requiring high reliability, robustness and long storage life. Conventional electrodes for thermal batteries are prepared by compacting powder mixtures into pellets. Separator is composed of halide mixture, such as LiCl-KCl eutectic salt, blended with MgO to immobilize the molten salt. In order to increase the power density and energy density, the resistance of electrolyte should be reduced because the resistance of electrolyte is predominant in thermal batteries. In this study, wetting behaviors and impregnation weight of molten salts as well as the micro structures of ceramic felt were investigated to be applicable to thin electrolyte. Discharge performances of single cell with the ceramic separator impregnated by molten salt were evaluated also. Zirconia felt with high porosity and large pore outperformed alumina felt in wetting characteristics and molten salt impregnation as well as discharge performances. Based on the results of this study, ceramic felt separator impregnated with molten salt have revealed as an alternative of conventional thick MgO based separator with no conspicuous sign of thermal runaway by short circuit.

In order to satisfy the needs for electrical power in future combat systems, a gasoline fuel processor (GFP) for an auxiliary power unit (APU) has been developed. This efficient design of a compact hydrogen-production system thermally and physically integrates the unit processes of autothermal reforming, high- and medium-temperature water gas shift, preferential oxidation, heat exchange and external burner into a single hardware package. The start-up strategy is established to turn the GFP on even at subzero temperature and reach the steady-state rapidly. In consideration of both energy consumption and system size, the sequence is initiated from start-burner mode. The catalytic-partial-oxidation (CPO) mode is second, followed by autothermal reforming (ATR). A glow-plug needed to ignite the gasoline is positioned behind the catalyst to minimize soot generation at start-burner mode. In ATR mode, feed rate of water for each heat exchanger is controlled to operate a reactor at target temperature and reduce the water condensation at surface of catalyst. Based on this start-up strategy, a GFP is able to produce a reformate gas that contained >40 vol.% H2 and

Effect of the addition of conductive carbonaceous materials to the FeS2 (pyrite) cathode on electrochemical performance of thermal battery is investigated by adding carbon blacks (CBs) or multi-walled carbon nanotubes (MWCNTs) which has conductive network structures with various amounts from 0.1 to 1 wt.%, compared to the amount of pure FeS2. Among the samples prepared with various amounts of CB or MWCNT addition, the 1 wt.% CB-added sample exhibits the highest electrochemical properties. These results suggest that the improvement in the electrochemical performance of thermal batteries can be achieved by the addition of the conductive carbonaceous materials to pyrite electrode.

has been widely used for cathode materials in thermal battery because of its high stability and current capability at high operation temperature. Salts such as a LiCl-KCl were added as a binder for improving electrical performance and formability of cathode powder. In this study, the effects of the addition of in LiCl-KCl binder on the formability of powder compact were investigated. With the increasing amount of addition to LiCl-KCl binder salts, the strength of the pressed compacts increased considerably when the powder mixture were pre-heat-treated above . The heat-treatment resulted in promoting the coating coverage of particles by the salts as was added. The observed coating as addition might be attributed to the enhanced wettability of the salt rather than its reduced melting temperature. The high strength of compacts by the addition and pre-heat-treatment could improve the formability of raw materials.

In this study, effects of pyrite () particle sizes on the electrochemical characteristics of thermal batteries are investigated using unit cells made of pulverized pyrite by ball-milling. At unit cell discharge test, the electrochemical capacity of pyrite-cell largely increases compared to pyrite-cell, and their internal resistances also decrease. These results are attributed to the increase in the active reaction area of pyrite by ball milling. However, at unit cell discharge test, a pyrite cell shows lower internal resistance than that of pyrite cell only at Z-phase region (). After that, a pyrite cell shows a decrease in the cell voltage and an rapid increase of the internal resistance in J-phase region () is observed compared to those of pyrite cell. It can be concluded that at the higher temperature, the thermally unstable pulverized pyrite is decomposed thermally as well as self discharged, simultaneously, which causes the higher resistance and lower capacity at in J-phase than that of pyrite cell.

Feasibility of utilizing unburned carbon residue in coal ash as a potential precursor for the production of activated carbon wasassessed to seek for solution to recycle unburned carbon residue. The unburned carbon concentrate generated from the 4 stagesof cleaner flotation has a grade of 87% carbon. The crystalline impurities in the concentrate included quartz and mullite.Unburned carbon had a low specific surface area of 10m 2 /g, which might be related to a high degree of coalification of domesticanthracite coal. Carbon particles were mostly porous and have a turbostratic structure. When 1g of carbon was activated with6g of KOH powder, the highest specific surface area value of 670m 2 /g was achieved. Low wettability of unburned carbon par-ticles, which was resulted from high temperature combustion in a boiler, might cause poor pore formation when they were acti-vated by KOH solution. The activated carbon produced in this study developed micropores, with an equivalent quality of * Received : November 5, 2013 · Revised : December 12, 2013 · Accepted : December 24, 2013Corresponding Author : Sujeong Lee (E-mail : crystal2@kigam.re.kr)Mineral Resources Research Division, Korea Institute of Geoscience & Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon,305-350 KoreaTel : +82-42-868-3125 / Fax : +82-42-868-3418ⓒThe Korean Institute of Resources Recycling. All rights reserved. This is an open-access article distributed under the termsof the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permitsunrestricted non-commercial use, distribution and reproduction in any medium, provided the original work is properly cited.

Microstructure and thermal stability of mechanically ball milled were investigated. The average particle size and distribution of powder were changed in two steps with the increased ball milling time. The average particle size drastically decreased from to 1.01 and after ball milling of 10 h and 30 h, respectively. However, the distribution was broad and a shoulder appeared at because the pulverization was still in process at 10 h ball milling. After 60 h ball milling, the distribution became narrower. After ball milling of 120 h, the average particle size increased because of particle agglomeration. Therefore, the particle size distribution became broaden again. Finally, after ball milling of 170 h, with the narrowest size distribution can be obtained. Thermal stability of was unstable as the particle was pulverized. Therefore, the activation energy of the fine size particles is 27% lower than that of the as-received .

A nanocomposite-carbon layer is coated onto the surface of 316L stainless steel (SS316) using a beam of accelerated C 60 ions at low temperature. The coating is composed of textured graphite nanocrystals ranging in size from 1 to 2 nm, with the graphene plane normal to the coating plane; the nanocrystals are separated by amorphous carbon. This orientation of the graphene layer provides low film resistivity in the direction of the substrate normal. Corrosion resistance tests performed in aggressive anodic and cathodic environments of a polymer electrolyte membrane fuel cell (PEMFC) show that the nanocomposite-carbon coated SS316L exhibits better anticorrosion properties than does bare SS316L. The interfacial contact resistance (ICR) of the nanocomposite-carbon coated SS316L is 12 mΩ cm 2 , which is similar to that of graphite at a compaction force of 150 N cm −2 and lower than a target of ∼20 mΩ cm 2 . A low value of ICR is maintained even after corrosion tests in aggressive anodic and cathodic environments. The fabricated nanocomposite-carbon coated SS316L exhibits excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.

The self-discharge of Zn anode material is identified as a main factor that can limit the energy density of alkaline Zn–air batteries. Al 2 O 3 has most positive effect on controlling the hydrogen evolution reaction accompanied by corroding Zn anode among various additives. The overpotential for hydrogen evolution is measured by potentio-dynamic polarization analysis. Al-oxide with high overpotential for hydrogen evolution reaction is uniformly coated on the surface of Zn powders via chemical solution process. The morphology and composition of the surface-treated and pristine Zn powders are characterized by SEM, EDS, XRD and XPS analyses. Aluminum is distributed homogeneously over the surface of modified Zn powders, indicating uniform coating of Al-oxide, and O1s and Al2 p spectra further identified surface coating layer to be the Al-oxide. The Al-oxide coating layer can prevent Zn from exposing to the KOH electrolyte, resulting in minimizing the side reactions within batteries. The 0.25 wt.% aluminum oxide coated Zn anode material provides discharging time of more than 10 h, while the pristine Zn anode delivers only 7 h at 25 mA cm −2 . Consequently, a surface-treated Zn electrode can reduce self-discharge which is induced by side reaction such as H 2 evolution, resulting in increasing discharge capacity.

Thermal batteries are primary batteries that use molten salts as an electrolyte and employ an internal pyrotechnic source to heat the battery stack to operating temperatures, typically between 450 and . The unit cell of thermal batteries consists of an anode, an electrolyte, a cathode, a heat pellet and a current collector. The heat source for such batteries is typically heat pellets based on . The elevated temperature by combustion of heat pellet is supposed to cause a flatness non-uniformity, buckling, with a lateral extension diameter of current collector. This paper mainly focused on the combustion and buckling model of current collector to simulate the effect of heat source. Mechanical stresses in the current collector caused by thermal stress is a critical design consideration of thermal batteries because the internal short circuit could be occurred.

Thermal batteries have excellent mechanical robustness, reliability, and long shelf life. Due to these characteristics as well as their unique activation mechanism, thermal batteries are widely adopted as military power sources. Li(Si)/ thermal batteries, which are used mostly in these days, use LiCl-KCl and LiBr-LiCl-LiF as molten salt electrolyte. However, it is known that Li(Si)/ thermal batteries have high internal resistance. Especially, cathode accounts for the greater part of internal resistance in unit cell. Many efforts have been put into to decrease the internal resistance of thermal batteries, which result in the development of new electrode material and new electrode manufacturing processes. But the applications of these new materials and processes are in some cases very expensive and need complicated additional processes. In this study, internal resistance study was conducted by adding carbon black and carbon nano-tube, which has high electron conductivity, into the cathode. As a results, it was found that the decrease of internal resistance of cathode by the addition of carbon black and carbon nano-tube.

A fuel cell/secondary battery hybrid power generation system could extend well beyond the efficiency and interoperability of the conventional diesel generator. The suggested power source system consists of 2.3 kW class PEMFC, 100 Ah lithium polymer battery, and two DC/DC converters by serial connection type. It was known that interoperability of sub-systems is the key factor for stable and optimal control of the hybrid power generation system. The modeling and simulation methods have been proposed to reduce the number of configurations and performance tests for components selection and select the optimized control condition of the power generation system. The control model for power source system is implemented based on the empirical formulation and carried out in the Matlab/Simulink environment. The results show that the simulation can be used to establish the algorism of prototype and increase the durability of the power source system.

All solid-state thin film battery was prepared with conventional sputtering technologies. Low conductivity of lithium phosphorus oxynitride (LiPON) electrolyte and higher resistance at the interface of LiCoO 2 /LiPON was crucial for the development of thin film battery. Presence of thermally treated Al 2 O 3 thin film at the interface of LiCoO 2 /LiPON decreased the interfacial resistance and increased the discharge capacity with the better cycling behaviors. Surface analysis and electrochemical impedance measurement indicate the formation of solid solution LiCo 1− y Al y O 2 at the interface of LiCoO 2 /LiPON.

The purpose of this paper is to introduce a way to deal with uncertainties in risk analysis. Risk analysis is a key process in security management in that its result provides a decision-basis for safeguard implementation. However, it must often rely on speculation, educated guesses, incomplete data, and many unproven assumptions. Users of risk analysis often provide their uncertain subjective opinions as input values to risk analysis. Therefore, the consideration of uncertainties in input data should be made when performing a risk analysis. As a tool for expressing and dealing with uncertainties in input data, we suggest the use of belief functions. Weprovide examples of how to use belief functions in qualitative risk analysis methods.