A Study on the Causal Relationship between Spot Price and Futures Price of Crude Oil and Agricultural Products

This paper studies the relationship between the agricultural, energy, and derivatives markets. This study empirically analyzes how the results of previous studies on the Granger causality between oil price and the spot price of agricultural products appear in the futures market by using the Toda and Yamamoto (1995)’ causality test. There are two main findings. First, 7 bidirectional causalities and 27 causalities between oil and 6 agricultural products are found, providing strong evidence of a causal relationship. Second, causality is found between oil prices and grain and oilseed type agricultural products, and the spot price of oil has relatively more causalities on agricultural product prices than the futures price of oil. Lastly, testing each period shows that a financial crisis can strengthen the relationship between the agriculture markets and the energy market

Energy-efficient CO2 hydrogenation with fast response using photoexcitation of CO2 adsorbed on metal catalysts.

Many heterogeneous catalytic reactions occur at high temperatures, which may cause large energy costs, poor safety, and thermal degradation of catalysts. Here, we propose a light-assisted surface reaction, which catalyze the surface reaction using both light and heat as an energy source. Conventional metal catalysts such as ruthenium, rhodium, platinum, nickel, and copper were tested for CO2 hydrogenation, and ruthenium showed the most distinct change upon light irradiation. CO2 was strongly adsorbed onto ruthenium surface, forming hybrid orbitals. The band gap energy was reduced significantly upon hybridization, enhancing CO2 dissociation. The light-assisted CO2 hydrogenation used only 37% of the total energy with which the CO2 hydrogenation occurred using only thermal energy. The CO2 conversion could be turned on and off completely with a response time of only 3 min, whereas conventional thermal reaction required hours. These unique features can be potentially used for on-demand fuel production with minimal energy input

Recent Developments in Synthesis and Photocatalytic Applications of Carbon Dots

The tunable photoluminescent and photocatalytic properties of carbon dots (CDs) via chemical surface modification have drawn increased attention to this emerging class of carbon nanomaterials. Herein, we summarize the advances in CD synthesis and modification, with a focus on surface functionalization, element doping, passivation, and nanocomposite formation with metal oxides, transition metal chalcogenides, or graphitic carbon nitrides. The effects of CD size and functionalization on photocatalytic properties are discussed, along with the photocatalytic applications of CDs in energy conversion, water splitting, hydrogen evolution, water treatment, and chemical degradation. In particular, the enzyme-mimetic and photodynamic applications of CDs for bio-related uses are thoroughly reviewed

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Department of Energy Engineering (Battery Science and Technology)With increasing demand for the application of conventional lithium-ion batteries (LIBs) to large-scale energy storage devices, associated safety concerns arising from the flammable organic liquid electrolytes (LEs) become more critical. Recently, all-solid-state lithium-ion batteries (ASLBs) using inorganic solid electrolytes (SEs) are considered a promising alternative to conventional LIBs in perspective of battery safety and energy density. Especially, sulfide SE materials are attracting great attention owing to high Li+ conductivities of 10-2-10-3 S cm-1 and deformability. From practical point of view, development of sheet-type electrodes and thin SE membranes are imperative for realizing practical high-energy all-solid-state cells. The solution-based process including polymeric components is common protocol for fabricating sheet-type electrodes in conventional LIBs. However, severe reactivity of sulfide SEs to common polar solvents and the particulate properties of these SEs lead to serious complications in the wet-slurry process for used to fabricate ASLB electrodes or SE membranes, such as the availability of solvents and polymeric binders and the formation of ionic contacts and percolation. In this work, a new scalable fabrication protocol for sheet-type ASLB is developed by solution-processable sulfide SEs (Li6PS5[Cl,Br]), combined with the conventional composite LIB electrodes or porous polymer membranes. Firstly, fabrication of the sheet-type ASLB electrode is demonstrated. The liquefied SE is infiltrated into the pores of LIB electrodes and then solidified, achieving high surface coverage of SE and favorable Li+ pathways. The SE-infiltrated LiCoO2 (LCO) and graphite (Gr) electrodes show high reversible capacities, which is comparable to LE-based cells and outperforms to conventional dry-mixed electrodes. The all-solid-state LCO/Gr full cells using SE-infiltrated electrodes demonstrate the promising electrochemical performance at both 30 ??C and 100 ??C, highlighting the excellent thermal stability of ASLBs. Moreover, sheet-type Si electrodes is fabricated and their electrochemical performance with variation of particle size of Si, polymeric binders, and external pressure is systematically investigated. Owing to intimate ionic contact by homogenous SE solution, the SE-infiltrated Si electrodes show high reversible capacities of over 3000 mA h g-1 and initial Coulombic efficiencies (CEs) over 80% at 30 ??C. The large difference in initial CEs between Si electrode with external pressure of 20 MPa and 5 MPa indicates the importance of engineering of external pressure. The high energy density of 338 W h kgLCO+Si-1 is achieved for the LCO/Si full cell, which is improved by 21% compared to that of LCO/Gr full cell. Finally, the flexible and thin (40-70 um) SE membranes are developed by combining solution-processable SEs (Li6PS5Cl0.5Br0.5 (LPSClBr)) with mechanically compliant and thermally stable polymer membranes (polyimide (PI)). The PI-LPSClBr membrane exhibits the Li+ conductivity of 0.2 mS cm-1 at 30 ??C with significantly reducing the mass loading of SE layer (5.0-9.5 mg cm-2 for PI-LPSClBr and 113 mg cm-2 for thick SE layer). The LiNi0.6Co0.2Mn0.2O2/graphite full cell using PI-LPSClBr shows promising electrochemical performance (at 30 ??C without liquid electrolytes) and excellent thermal stability, outperforming the ASLBs using composite solid electrolyte (PEO-LiTFSI including inorganic filler). Finally, the SE injection process, similar to liquid electrolyte injection in conventional LIBs, is successfully demonstrated.clos

Singlet Fermionic Dark Matter with Dark ZZ

We present a fermionic dark matter model mediated by the hidden gauge boson. We assume the QED-like hidden sector which consists of a Dirac fermion and U(1)$_X$ gauge symmetry, and introduce an additional scalar electroweak doublet field with the U(1)$_X$ charge as a mediator. The hidden U(1)$_X$ symmetry is spontaneously broken by the electroweak symmetry breaking and there exists a massive extra neutral gauge boson in this model which is the mediator between the hidden and visible sectors. Due to the U(1)$_X$ charge, the additional scalar doublet does not couple to the Standard Model fermions, which leads to the Higgs sector of type I two Higgs doublet model. The new gauge boson couples to the Standard Model fermions with couplings proportional to those of the ordinary $Z$ boson but very suppressed, thus we call it the dark $Z$ boson. We study the phenomenology of the dark $Z$ boson and the Higgs sector, and show the hidden fermion can be the dark matter candidate.Comment: 10 pages, 3 figure