Cities worldwide are attempting to transform themselves into smart cities. Recent cases and studies show that a key factor in this transformation is the use of urban big data from stakeholders and ...physical objects in cities. However, the knowledge and framework for data use for smart cities remain relatively unknown. This paper reports findings from an analysis of various use cases of big data in cities worldwide and the authors' four projects with government organizations toward developing smart cities. Specifically, this paper classifies the urban data use cases into four reference models and identifies six challenges in transforming data into information for smart cities. Furthermore, building upon the relevant literature, this paper proposes five considerations for addressing the challenges in implementing the reference models in real-world applications. The reference models, challenges, and considerations collectively form a framework for data use for smart cities. This paper will contribute to urban planning and policy development in the modern data-rich economy.
•We analyze and classify urban data use cases into four reference models.•We identify six challenges in transforming data into information for smart cities.•We give five considerations to address the challenges in implementing the models.•The challenges and considerations are based on four action research projects with government.•Our findings can aid urban planning and policy development in a data-rich economy.
Sodium (Na) ion batteries are interesting candidates for replacing lithium (Li) ion batteries, primarily due to the abundance of Na in the environment. However, the performance and energy density of ...a Na-ion battery are inferior to those of a Li-ion battery. Organic active materials can help overcome the drawbacks associated with Na-ion batteries because of their many advantages. However, such organic polymer electrodes are subjected to a high self-discharge and low practical capacity because the polymer electrode easily dissolves in an organic electrolyte and forms an insulating layer. Therefore, in this study, we have designed a unique organic electrode in which an active polymer is encapsulated into a carbon nanotube (CNT) to form an electrode with high polymer content. The CNT is able to retain the active polymer within the electrode structure, providing an effective electronic conduction path. Moreover, the CNT can contain large amounts of active polymer and therefore exhibits superior electrochemical properties without self-discharge, making it well suited for use as a cathode material in a Na-ion battery.
How to deal with nonignorable response is often a challenging problem encountered in statistical analysis with missing data. Parametric model assumption for the response mechanism is sensitive to ...model misspecification. We consider a semiparametric response model that relaxes the parametric model assumption in the response mechanism. Two types of efficient estimators, profile maximum likelihood estimator and profile calibration estimator, are proposed, and their asymptotic properties are investigated. Two extensive simulation studies are used to compare with some existing methods. We present an application of our method using data from the Korean Labor and Income Panel Survey.
Rechargeable organic batteries constitute a promising alternative to lithium ion batteries because of the abundance of the necessary raw materials, their lightness, environmental friendliness, high ...flexibility, and high capacity. However, organic batteries present problems of low conductivity and the instability of their liquid electrolytes. PTMA-impregnated CMK-3 (PTMA/CMK-3) is successfully used as a novel electrode to solve the problems associated with organic batteries. The PTMA/CMK-3 has a theoretical capacity of 111 mAh g−1 with a single-step, single-redox reaction between the nitroxide radical and oxoammonium cation (3.0–4.0 V cut-off) and a theoretical capacity of 222 mAh g−1 with a two-step double-redox reaction between the aminoxy anion and oxoammonium cation (1.5–4.0 V cut-off). Although the PTMA/CMK-3 cells deliver an initial discharge capacity of 110.9 mAh g−1 with the single-redox reaction and 219.8 mAh g−1 with the double-redox at 1 C-rate (which is almost equal to the theoretical capacity), the capacity retentions at the 1000th cycle are 80.7% and 29.3%, respectively. The high degradation associated with the double-redox reaction is ascribed to the irreversible reaction of the aminoxy anion. The resolution of the irreversibility of the aminoxy anion could lead to the commercialization of nitroxide radical-based organic batteries.
Display omitted
•PTMA-impregnated CMK-3 is successfully synthesized for organic battery.•PTMA/CMK-3 electrodes show high initial discharge capacity.•Single- and double-redox reaction of PTMA/CMK-3 cells are compared.•Double-redox reaction has an irreversible reaction of the aminoxy anion.
Development of Na-ion battery electrolyte with high-performance electrochemical properties and high safety is still challenging to achieve. In this study, we report on a NASICON (Na sub(3)Zr sub(2)Si ...sub(2 )PO sub(12))-based composite hybrid solid electrolyte (HSE) designed for use in a high safety solid-state sodium battery for the first time. The composite HSE design yields the required solid-state electrolyte properties for this application, including high ionic conductivity, a wide electrochemical window, and high thermal stability. The solid-state batteries of half-cell type exhibit an initial discharge capacity of 330 and 131 mA h g super(-1) for a hard carbon anode and a NaFePO sub(4) cathode at a 0.2C-rate of room temperature, respectively. Moreover, a pouch-type flexible solid-state full-cell comprising hard carbon/HSE/NaFePO sub(4) exhibits a highly reversible electrochemical reaction, high specific capacity, and a good, stable cycle life with high flexibility.
Low Coulombic efficiency and significant capacity decay resulting from an unstable solid electrolyte interphase (SEI) and dendritic growth pose challenges to the practical application of ...lithium‐metal batteries. In this study, a highly efficient protection layer induced by octaphenylsilsesquioxane (OPS) with LiFSI salt is investigated. The OPS exhibits a strong adsorption energy with lithium, its multi‐site gradient adsorption ability enables the simultaneous capture of 8 Li+ and the uniform regulation of Li ion flux. Moreover, the mechanical strength and electronic insulation of the OPS layer induces Li deposition under the protection layer and effectively inhibits lithium dendrite growth. Such a protection layer contributes to the stable and dendrite‐free performance of a lithium‐metal battery employing LiNi0.8Co0.1Mn0.1O2 (NCM811) as a cathode and an ultrathin OPS‐protected lithium foil (20 µm) as the anode. A remarkable capacity retention of 91.4% is achieved after 300 cycles at 1C. The OPS‐protected Li anodes and NCM811 are also tested in combination with a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte, showing extended cyclability up to 300 cycles with an average Coulombic efficiency of 99.58% and capacity retention of 85.7%.
A siloxane‐based protective layer is demonstrated for efficient and stable lithium‐metal anodes. By virtue of the multi‐site gradient adsorption ability of Li, it effectively promotes homogeneous lithium‐ion flux, prohibits side reactions, and suppresses dendrite formation, significantly improving the cycling performance of Li/ LiNi0.8Co0.1Mn0.1O2 batteries.
A hybrid nanofiber PVDF-HFP polymer matrix with dispersed SiO2 nanoparticles was prepared by electrospinning, and 1M lithium bis(trifluoromethysulfonyl)imide (LiTFSI)/1-propyl-3-methylimidazolium ...bis(trifluoromethysulfonyl)imide (PMImTFSI) was incorporated in the hybrid polymer matrix to produce a polymer gel electrolyte for lithium-sulfur batteries. The PMImTFSI-based hybrid gel polymer electrolyte (ILGPE) reduced the concentration of Li+-coordinated TFSI, and the incorporation of PMImTFSI increased the α-phase content of PVDF-HFP, reducing polymer crystallinity. In addition, ILGPE showed high ionic conductivity, high oxidation potential (>5.0V vs. Li/Li+), and low flammability. The Li/S battery utilizing ILGPE showed a high initial discharge capacity of 1029mAhg–1 and maintained a stable capacity of 885mAhg–1 after 30 cycles at a current rate of 0.1C.
Display omitted
•A hybrid nanofiber polymer matrix with dispersed SiO2 nanoparticles was prepared by electrospinning.•ILGPE showed high ionic conductivity, high oxidation potential, and low flammability.•The Li/S battery utilizing ILGPE showed a good electrochemical performance.
Lithium batteries occupy the large‐scale electric mobility market raising concerns about the environmental impact of cell production, especially regarding the use of poly(vinylidene difluoride) ...(teratogenic) and N‐methyl‐2‐pyrrolidone (NMP, harmful). To avoid their use, an aqueous electrode processing route is utilized in which a water‐soluble hybrid acrylic‐fluoropolymer together with sodium carboxymethyl cellulose is used as binder, and a thin phosphate coating layer is in situ formed on the surface of the nickel‐rich cathode during electrode processing. The resulting electrodes achieve a comparable performance to that of NMP‐based electrodes in conventional organic carbonate‐based electrolyte (LP30). Subsequently, an ionic liquid electrolyte (ILE) is employed to replace the organic electrolyte, building stable electrode/electrolyte interphases on the surface of the nickel‐rich positive electrode (cathode) and metallic lithium negative electrode (anode). In such ILE, the aqueously processed electrodes achieve high cycling stability with a capacity retention of 91% after 1000 cycles (20 °C). In addition, a high capacity of more than 2.5 mAh cm–2 is achieved for high loading electrodes (≈15 mg cm–2) by using a modified ILE with 5% vinylene carbonate additive. A path to achieve environmentally friendly electrode manufacturing while maintaining their outstanding performance and structural integrity is demonstrated.
Positive electrodes composed of high nickel content active material and aqueous binder offer remarkable cycling stability and high capacity (2.5 mAh cm–2) at high loadings in a poorly flammable ionic liquid electrolyte demonstrating a path toward environmentally friendly electrode manufacturing for lithium metal batteries.
Rechargeable lithium batteries are attractive power sources for electronicdevices and are being aggressively developed for vehicular use. Nevertheless,problems with their safety and reliability must ...be solved for the large-scale useof lithium batteries in transportation and grid-storage applications. In this study,a unique hybrid solid-state electrolyte composed of an ionic liquid electrolyte（LiTFSI/Pyr14TFSI） and BaTiO3 nanosize ceramic particles was prepared withouta polymer. The electrolyte exhibited high thermal stability, a wide electrochemicalwindow, good ionic conductivity of 1.3×10-3 S-cm-1 at 30 ℃, and a remarkably highlithium-ion transference number of 0.35. The solid-state LiFePO4 cell exhibited thebest electrochemical properties among the reported solid-state batteries, along witha reasonable rate capability. Li/LiCoO2 cells prepared using this nanocompositesolid electrolyte exhibited high performance at both room temperature and a hightemperature, confirming their potential as lithium batteries with enhanced safetyand a wide range of oDerating temrperatures.
Summary
The statistical challenges in using big data for making valid statistical inference in the finite population have been well documented in literature. These challenges are due primarily to ...statistical bias arising from under‐coverage in the big data source to represent the population of interest and measurement errors in the variables available in the data set. By stratifying the population into a big data stratum and a missing data stratum, we can estimate the missing data stratum by using a fully responding probability sample and hence the population as a whole by using a data integration estimator. By expressing the data integration estimator as a regression estimator, we can handle measurement errors in the variables in big data and also in the probability sample. We also propose a fully nonparametric classification method for identifying the overlapping units and develop a bias‐corrected data integration estimator under misclassification errors. Finally, we develop a two‐step regression data integration estimator to deal with measurement errors in the probability sample. An advantage of the approach advocated in this paper is that we do not have to make unrealistic missing‐at‐random assumptions for the methods to work. The proposed method is applied to the real data example using 2015–2016 Australian Agricultural Census data.
PDF
