National Chung Cheng University

Nguyen V., Lin P., Cheng B., Hwang R., Lin Y.

Sixth-generation (6G) mobile networks will have to cope with diverse threats on a space-air-ground integrated network environment, novel technologies, and an accessible user information explosion. However, for now, security and privacy issues for 6G remain largely in concept. This survey provides a systematic overview of security and privacy issues based on prospective technologies for 6G in the physical, connection, and service layers, as well as through lessons learned from the failures of existing security architectures and state-of-the-art defenses. Two key lessons learned are as follows. First, other than inheriting vulnerabilities from the previous generations, 6G has new threat vectors from new radio technologies, such as the exposed location of radio stripes in ultra-massive MIMO systems at Terahertz bands and attacks against pervasive intelligence. Second, physical layer protection, deep network slicing, quantum-safe communications, artificial intelligence (AI) security, platform-agnostic security, real-time adaptive security, and novel data protection mechanisms such as distributed ledgers and differential privacy are the top promising techniques to mitigate the attack magnitude and personal data breaches substantially.

Sun H., Zhu G., Zhu Y., Lin M., Chen H., Li Y., Hung W.H., Zhou B., Wang X., Bai Y., Gu M., Huang C., Tai H., Xu X., Angell M., et. al.

Rechargeable lithium metal batteries are next generation energy storage devices with high energy density, but face challenges in achieving high energy density, high safety, and long cycle life. Here, lithium metal batteries in a novel nonflammable ionic-liquid (IL) electrolyte composed of 1-ethyl-3-methylimidazolium (EMIm) cations and high-concentration bis(fluorosulfonyl)imide (FSI) anions, with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a key additive are reported. The Na ion participates in the formation of hybrid passivation interphases and contributes to dendrite-free Li deposition and reversible cathode electrochemistry. The electrolyte of low viscosity allows practically useful cathode mass loading up to ≈16 mg cm-2 . Li anodes paired with lithium cobalt oxide (LiCoO2 ) and lithium nickel cobalt manganese oxide (LiNi0.8 Co0.1 Mn0.1 O2 , NCM 811) cathodes exhibit 99.6-99.9% Coulombic efficiencies, high discharge voltages up to 4.4 V, high specific capacity and energy density up to ≈199 mAh g-1 and ≈765 Wh kg-1 respectively, with impressive cycling performances over up to 1200 cycles. Highly stable passivation interphases formed on both electrodes in the novel IL electrolyte are the key to highly reversible lithium metal batteries, especially for Li-NMC 811 full batteries.

Wu I., Chiu M., Chen K.

• Online consumers are both system users and impulse buyers for using e-stores. • A model is proposed with three issues, perceived risk, ECM, and flow state. • Perceived risk has a negative effect on perceived usefulness (PU) and satisfaction. • In ECM, e-store confirmation is important for link to PU and is not to satisfaction. • Flow state is an important concern for raising impulse buying behavior. Since much online shopping is attributed to online impulse buying, it is important to define this particular shopping process. This process has three important issues, perceived risk for virtual stores as well as e-store design and psychological state for online shopping. This is because consumers are both system users and impulse buyers when shopping on e-stores. E-store design is based on the interaction of customers with e-stores and the expectation-confirmation model supports examination of this issue with a wide familiarity in IT use. Psychological state is emotional responses to the stimulus of products in e-stores and flow theory, with task skill and task challenge as precursors, is suitable for exploring this issue. Grounding on the three issues, this study proposes a new research model with these considerations to thoroughly examine the determinants of online impulse buying. Flow state and customer satisfaction also interact with each other. Empirical research shows an important link for the three defined issues of online impulse buying.

Liu X., Wu T., Chen J., Meng X., He X., Noda T., Chen H., Yang X., Segawa H., Wang Y., Han L.

We report a templated growth of FASnI3 crystals by reconstruction of the intermediate phase, and an efficiency of 11.22% was certified.

Hwang R., Peng M., Huang C., Lin P., Nguyen V.

Various attacks have emerged as the major threats to the success of a connected world like the Internet of Things (IoT), in which billions of devices interact with each other to facilitate human life. By exploiting the vulnerabilities of cheap and insecure devices such as IP cameras, an attacker can create hundreds of thousands of zombie devices and then launch massive volume attacks to take down any target. For example, in 2016, a record large-scale DDoS attack launched by millions of Mirai-injected IP cameras and smart printers blocked the accessibility of several high-profile websites. To date, the state-of-the-art defense systems against such attacks rely mostly on pre-defined features extracted from the entire flows or signatures. The feature definitions are manual, and it would be too late to block a malicious flow after extracting the flow features. In this work, we present an effective anomaly traffic detection mechanism, namely D-PACK, which consists of a Convolutional Neural Network (CNN) and an unsupervised deep learning model (e.g., Autoencoder) for auto-profiling the traffic patterns and filtering abnormal traffic. Notably, D-PACK inspects only the first few bytes of the first few packets in each flow for early detection. Our experimental results show that, by examining just the first two packets in each flow, D-PACK still performs with nearly 100% accuracy, while features an extremely low false-positive rate, e.g., 0.83%. The design can inspire the emerging efforts towards online anomaly detection systems that feature reducing the volume of processed packets and blocking malicious flows in time.

Zhu G., Tian X., Tai H., Li Y., Li J., Sun H., Liang P., Angell M., Huang C., Ku C., Hung W., Jiang S., Meng Y., Chen H., Lin M., et. al.

Lithium-ion batteries (LIBs) are widely used in applications ranging from electric vehicles to wearable devices. Before the invention of secondary LIBs, the primary lithium-thionyl chloride (Li-SOCl2) battery was developed in the 1970s using SOCl2 as the catholyte, lithium metal as the anode and amorphous carbon as the cathode1–7. This battery discharges by lithium oxidation and catholyte reduction to sulfur, sulfur dioxide and lithium chloride, is well known for its high energy density and is widely used in real-world applications; however, it has not been made rechargeable since its invention8–13. Here we show that with a highly microporous carbon positive electrode, a starting electrolyte composed of aluminium chloride in SOCl2 with fluoride-based additives, and either sodium or lithium as the negative electrode, we can produce a rechargeable Na/Cl2 or Li/Cl2 battery operating via redox between mainly Cl2/Cl− in the micropores of carbon and Na/Na+ or Li/Li+ redox on the sodium or lithium metal. The reversible Cl2/NaCl or Cl2/LiCl redox in the microporous carbon affords rechargeability at the positive electrode side and the thin alkali-fluoride-doped alkali-chloride solid electrolyte interface stabilizes the negative electrode, both are critical to secondary alkali-metal/Cl2 batteries. Rechargeable Na/Cl2 and Li/Cl2 batteries are produced with a microporous carbon positive electrode, aluminium chloride in thionyl chloride as the electrolyte, and either sodium or lithium as the negative electrode.

Zhang X., Li J., Li Y., Jung Y., Kuang Y., Zhu G., Liang Y., Dai H.

Reducing CO2 to value-added multicarbon (C2+) fuels and chemicals using renewable energy is a viable way to circumvent CO2 buildup in the atmosphere and facilitate closing the carbon cycle. To date it remains a challenge to achieve high product selectivity and long-term stability of electrocatalytic carbon dioxide reduction reaction (CO2RR) especially at practically relevant high current levels >100 mA cm-2. Here, we report a simple electrodeposited Cu electrocatalyst on a hydrophobic porous gas-diffusion layer (GDL) electrode affording stable and selective CO2RR to C2+ products in near-neutral KCl electrolytes. By directing the CO2 stream to fully submerged hydrophobic GDLs in a H-cell, high C2+ partial current densities near 100 mA cm-2 were achieved. In a flow-cell setup, the Cu/GDL cathode in 2 M KCl afforded stable CO2RR superior to that in widely used KOH electrolytes. We found that Cu etching/corrosion associated with trace oxygen played a role in the catalyst instability in alkaline media under cathodic CO2RR conditions, a problem largely suppressed in near-neutral electrolyte. A two-electrode CO2 electrolyzer was constructed with a Cu/GDL cathode in KCl catholyte and an anode comprised of nickel-iron hydroxide on nickel foam (NiFe/NF) in a KOH anolyte separated by Nafion membrane. By periodically adding HCl to the KCl catholyte to compensate the increasing pH and remove accumulated (bi)carbonates, we observed little decay over ∼30 h in flow-cell CO2RR activity and selectivity at 150 mA cm-2 with a high Faradaic efficiency (FE) of ∼75% and energy efficiency of 40% for C2+ products.

Bundschuh J., Schneider J., Alam M.A., Niazi N.K., Herath I., Parvez F., Tomaszewska B., Guilherme L.R., Maity J.P., López D.L., Cirelli A.F., Pérez-Carrera A., Morales-Simfors N., Alarcón-Herrera M.T., Baisch P., et. al.

This review presents a holistic overview of the occurrence, mobilization, and pathways of arsenic (As) from predominantly geogenic sources into different near-surface environmental compartments, together with the respective reported or potential impacts on human health in Latin America. The main sources and pathways of As pollution in this region include: (i) volcanism and geothermalism: (a) volcanic rocks, fluids (e.g., gases) and ash, including large-scale transport of the latter through different mechanisms, (b) geothermal fluids and their exploitation; (ii) natural lixiviation and accelerated mobilization from (mostly sulfidic) metal ore deposits by mining and related activities; (iii) coal deposits and their exploitation; (iv) hydrocarbon reservoirs and co-produced water during exploitation; (v) solute and sediment transport through rivers to the sea; (vi) atmospheric As (dust and aerosol); and (vii) As exposure through geophagy and involuntary ingestion. The two most important and well-recognized sources and mechanisms for As release into the Latin American population's environments are: (i) volcanism and geothermalism, and (ii) strongly accelerated As release from geogenic sources by mining and related activities. Several new analyses from As-endemic areas of Latin America emphasize that As-related mortality and morbidity continue to rise even after decadal efforts towards lowering As exposure. Several public health regulatory institutions have classified As and its compounds as carcinogenic chemicals, as As uptake can affect several organ systems, viz. dermal, gastrointestinal, peptic, neurological, respiratory, reproductive, following exposure. Accordingly, ingesting large amounts of As can damage the stomach, kidneys, liver, heart, and nervous system; and, in severe cases, may cause death. Moreover, breathing air with high As levels can cause lung damage, shortness of breath, chest pain, and cough. Further, As compounds, being corrosive, can also cause skin lesions or damage eyes, and long-term exposure to As can lead to cancer development in several organs. • Arsenic (As) mobilization from geogenic and anthropic sources to near-surface environments • Different pathways of As human exposure and their health impacts with Latin American examples • Natural dissemination of As in surrounding environments through leaching of As bearing rocks • Acceleration of natural dissemination of As through mining of metallic and energy resources • (Hydro)(bio)geochemical processes during As exposure through drinking water and food chain • Health issues associated with As uptake following intake through indigestion and inhalation

Lien S., Deng D., Lin C., Tsai H., Chen T., Guo C., Cheng S.

Featuring direct communications between two user equipments (UEs) without signal relay through a base station, 3GPP sidelink transmissions have manifested their crucial roles in the Long-Term Evolution (LTE) Advanced (LTE-A) for public safety and vehicle-to-everything (V2X) services. With this successful development in LTE-A, the evolution of sidelink transmissions continues in 3GPP New Radio (NR), which renders sidelink an inevitable component as well as downlink and uplink. Targeting at offering low latency, high reliability and high throughout V2X services for advanced driving use cases, a number of new sidelink functions not provided in the LTE-A are supported in NR, including the feedback channel, grant-free access, enhanced channel sensing procedure, and new control channel design. To fully comprehend these new functions, this paper therefore provides essential knowledge of 3GPP NR sidelink transmissions, including the physical layer structure, resource allocation mechanisms, resource sensing and selection procedures, synchronization, and quality-of-service (QoS) management. Furthermore, this paper also provides performance evaluation to assess the gains brought from the new control channel design. As NR sidelink transmissions have been regarded as a foundation to provide advanced services other than V2X in future releases (e.g., advanced relay), potential enhancements are also discussed to serve the urgent demand in corresponding normative works.

Venkatesan M., Veeramuthu L., Liang F., Chen W., Cho C., Chen C., Chen J., Yan Y., Chang S., Kuo C.

Heavy metal and other toxicant detection in natural resources like water, air, soil and food is vital for environmental safety, personal hygiene, and public health care. Abundant number of sensor has acquired its wide and pivotal role in establishing the peaceful and healthy environments. The reliable features such as detection range, response/recovery time, stability and portability is in its urgency for achieving its lifetime applicability. For ultrasensitive chemosensory applications, colorimetric and fluorescent nanofibers engender a linear range, the lowest detection limit, and faster response toward harmful toxic pollutants such as heavy metals and other toxicants including gases, pH, temperature, humidity, and cancer cells. In this review, we surveyed various modes of sensing, sensor fabrication and the evolution of naked eye visible color optical sensors developed with electrospun nanofibrous membranes along with their strength and weaknesses. The review outlines the obstacles, trends and breakthroughs achieved in optical sensory nanofibers and it will definitely inspire the research community in recognizing and overcoming the interdisciplinary challenges to achieve the cleaner greener environment.