PySDTest: a Python Package for Stochastic Dominance Tests

We introduce PySDTest, a Python package for statistical tests of stochastic dominance. PySDTest can implement the testing procedures of Barrett and Donald (2003), Linton et al. (2005), Linton et al. (2010), Donald and Hsu (2016), and their extensions. PySDTest provides several options to compute the critical values including bootstrap, subsampling, and numerical delta methods. In addition, PySDTest allows various notions of the stochastic dominance hypothesis, including stochastic maximality among multiple prospects and prospect dominance. We briefly give an overview of the concepts of stochastic dominance and testing methods. We then provide a practical guidance for using PySDTest. For an empirical illustration, we apply PySDTest to the portfolio choice problem between the daily returns of Bitcoin and S&P 500 index. We find that the S&P 500 index returns second-order stochastically dominate the Bitcoin returns

High-Power Hybrid Solid-State Lithium-Metal Batteries Enabled by Preferred Directional Lithium Growth Mechanism

Solid electrolytes are revolutionizing the field of lithium-metal batteries; however, their practical implementa-tion has been impeded by the interfacial instability between lithium metal electrodes and solid electrolytes. While various interlayers have been suggested to address this issue in recent years, long-term stability with repeated lithium deposition/ stripping has been challenging to attain. Herein, we successfully operate a high-power lithium-metal battery by inducing the preferred directional lithium growth with a rationally designed interlayer, which employs (i) crystalline-direction-controlled carbon material providing isotropic lithium transports, with (ii) prelithium deposits that guide the lithium nucleation direction toward the current collector. This combination ensures that the morphology of the interlayer is mechanically robust while regulating the preferred lithium growth underneath the interlayer without disrupting the initial interlayer/electrolyte interface, enhancing the durability of the interface. We illustrate how these material/geometric optimizations are conducted from the thermodynamic considerations, and its applicability is demonstrated for the garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes paired with the capacity cathode. It is shown that a lithium-metal cell with the optimized amorphous carbon interlayer with prelithium deposits exhibits outstanding room-temperature cycling performance (99. 6% capacity retention after 250 cycles), delivering 4.0 mAh cm-2 at 2.5 mA cm-2 without significant degradation of the capacity. The successful long-term operation of the hybrid solid-state cell at room temperature (approximately a cumulative deliverable capacity of over 1000 mAh cm-2) is unprecedented and records the highest performance reported for lithium-metal batteries with LLZO electrolytes until date

High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm(-2) cathode delivers a cumulative capacity of over 4000 mAh cm(-2) at 3 mA cm(-2), which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the development of solid-state Li-metal batteries by highlighting the efficacy of the coupled bulk and interface doping of solid electrolytes. Lithium-metal batteries (LMBs) have attracted intense interest but the instability issues limit its practical deployment. Here, the authors report a durable LMB with high energy density using a garnet-type solid electrolyte with a tailored Li-metal compatibility

First snapshot on behavioral characteristics and related factors of patients with chronic kidney disease in South Korea during the COVID-19 pandemic (June to October 2020)

Background The recent novel coronavirus disease 2019 (COVID-19) pandemic has led to unprecedented changes in behavior. We evaluated the current status of precautionary behavior and physical activity in chronic kidney disease (CKD) patients during the COVID-19 pandemic. Methods A population of CKD patients (n = 306) registered in the Study on Kidney Disease and Environmental Chemicals (SKETCH, Clinical Trial No. NCT04679168) cohort recruited from June 2020 to October 2020 was included in the study. We conducted a questionnaire survey related to risk perception of COVID-19, precautionary behavior, and physical activity. Results There were 187 patients (61.1%) with estimated glomerular filtration rate of <45 mL/min/1.73 m2. This population showed a higher degree of risk perception for COVID-19 than the general population. Age was the most significant determinant of risk perception among CKD patients. During the pandemic, social distancing and hygiene-related behavior were significantly increased (p < 0.001). The frequency of exercise was decreased only in those who took regular exercise, without diabetes, or with a lower Charlson comorbidity index (CCI) (p < 0.001), with no change among the other groups. Socioeconomic status and comorbidities significantly affected behavioral characteristics regardless of the category. Education and income were significantly associated with precautionary behaviors such as staying at home and hand sanitizer use. Patients with higher CCI status significantly increased frequency of exercise (adjusted odds ratio, 2.10; 95% confidence interval, 1.01–4.38). Conclusion CKD patients showed higher risk perception with active precautionary behavioral changes than the general population. Healthcare providers should be aware of the characteristics to comprise precautionary behavior without reducing physical activity

Testing for time stochastic dominance

© 2022 Elsevier B.V.We propose nonparametric tests for the null hypothesis of time stochastic dominance. Time stochastic dominance makes a partial order of different prospects over time based on the net present value criteria for general utility and time discount function classes. For example, time stochastic dominance can be used for ranking investment strategies or environmental policies based on the expected net present value of the future benefits. We consider an Lp-type test statistic and derive its large sample distribution under standard panel data sampling scheme with fixed time dimension. We suggest a path-wise (or cluster) bootstrap procedure that allows individual time series dependence over the time horizon. We describe two approaches, the contact-set approach and the numerical delta method, that may lead to enhanced power compared to the conventional least-favorable-case based approach. We prove the asymptotic validity of our testing procedures. We investigate the finite sample performance of the tests in simulation studies. As an illustration, we apply the proposed tests to evaluate the Million Baht Village Fund Program in Thailand and carbon emission trading scheme in China.N

Investigation on the interface between Li10GeP2S12 electrolyte and carbon conductive agents in all-solid-state lithium battery

All-solid-state batteries are considered as one of the attractive alternatives to conventional lithium-ion batteries, due to their intrinsic safe properties benefiting from the use of non-flammable solid electrolytes in ASSBs. However, one of the issues in employing the solid-state electrolyte is the sluggish ion transport kinetics arising from the chemical and physical instability of the interfaces among solid components including electrode material, electrolyte and additive agents. In this work, we investigate the stability of the interface between carbon conductive agents and Li10GeP2S12 in a composite cathode and its effect on the electrochemical performance of ASSBs. It is found that the inclusion of various carbon conductive agents in composite cathode leads to inferior kinetic performance of the cathode despite expectedly enhanced electrical conductivity of the composite. We observe that the poor kinetic performance is attributed to a large interfacial impedance which is gradually developed upon the inclusions of the various carbon conductive agents regardless of their physical differences. The analysis through X-ray Photoelectron Spectroscopy suggests that the carbon additives in the composite cathode stimulate the electrochemical decomposition of LGPS electrolyte degrading its surface during cycling, indicating the large interfacial resistance stems from the undesirable decomposition of the electrolyte at the interface. © The Author(s) 20181

Challenges and Strategies towards Practically Feasible Solid-State Lithium Metal Batteries

© 2021 Wiley-VCH GmbHRemarkable improvement of the ionic conductivity of inorganic solid electrolytes (SEs) exceeding 10 mS cm−1 at room temperature has opened up the opportunities to realize the commercialization of solid-state batteries (SSBs). The transition to the intrinsically inflammable SEs also promises that SSBs would successfully utilize lithium metal anode thus achieving the high-energy-density lithium metal batteries without the risk of a safety hazard. However, the practical operation of solid-state lithium metal batteries (SSLMBs) still faces the challenges of the poor cycle stability and the low energy efficiency, which are coupled with the interface stability and even with the dendrite growth of lithium metal. This article overviews current understandings regarding the underlying origins of the issues in employing the lithium metal anode in SSLMBs from the five main standpoints: i) the chemical/electrochemical interfacial stability, ii) the microscopic evolution of interfacial morphology, iii) the intrinsic diffusivity of lithium atom/vacancy at the interface, iv) imperfections (defect/pores), and v) non-negligible electronic conductivity of SEs. The discussions are followed on the state-of-the-art efforts and strategies to overcome these respective challenges. Finally, the authors provide their perspectives for the future research directions toward achieving the commercial level of high-energy SSLMBs.11Nsciescopu

Progress in the development of sodium-ion solid electrolytes

The development of safe, reliable, yet economical energy storage has been reemphasized with recent incidents involving the explosion and subsequent recall of lithium-ion batteries. The organic liquid electrolyte used in the conventional lithium-ion battery can potentially act as a fuel for combustion in a thermal-runaway reaction, and hence an alternative with a significantly reduced flammability must be sought. All-solid-state batteries have the potential to meet safety and reliability requirements with the possibility of increasing the volumetric energy density of the system, making these a promising candidate for the development of the next generation of energy storage. Moreover, the sodium-ion battery exhibits a better cost-efficiency without significantly compromising the energy density, making the combination of the sodium chemistry with the solid electrolyte an attractive choice for safe and economical energy storage. Here, a general background on the recent development of ceramic and glass-ceramic sodium-ion-conducting electrolytes is provided with regard to oxide-,sulfide-, and hydride-based electrolytes. The ionic conductivity, chemical stability, and mechanical properties of the sodium-based solid electrolyte are discussed, which is followed by a perspective on future developments in the field.