Assortment Size and Performance of Online Sellers: An Inverted U-Shaped Relationship

This paper investigates the role of assortment size in sellers’ performance in the e-commerce context, which has been primarily associated with lowered search costs and switching costs. However, in contrast to the findings in the literature, our theoretical analysis postulates an inverted U-shaped association, showing that performance of online sellers increases and then decreases as the assortment size becomes larger. The nonlinear effect can be effectively explained by the interplay between the benefits derived from simultaneous consumer utility and the liabilities derived from the competition-intensifying effect. Additionally, the optimal level of assortment size is reduced when market density or product uncertainty is high. Using a data set of 10,000 online sellers from a large e-commerce platform, our hypotheses concerning the inverted U-shaped curve and moderation effects of market density and product uncertainty are statistically supported. Our research contributes to the assortment literature by revealing the special effects of assortment size in the online retailing context, and provides practical implications for online sellers’ assortment planning and optimization under both general settings and specific conditions

“GROWTH OF THE FITTER”: EVOLUTIONARY GROWTH PATHS AND FIRM SIZE OF START-UPS IN E-MARKETS

Existing research related to firm growth has not paid sufficient attention to the growth paths of online stores in e-markets. The linkage between growth path and firm size has not been built up. This paper aims to investigate evolutionary trajectories and their effects on firm size. Theoretically, conceptually define three types of distinguishable paths, namely the convergent, tepid, and sustained paths. We then propose related theoretical hypotheses that reflect the impacts of different types of growth paths on the resulting firm size. To empirically validate the proposed hypotheses, we applied the trajectory analysis method with a novel indicator, the relative expansion rate, based on a data set that consists of 5,582 online stores on Taobao.com, the largest e-commerce platform in the world. Testing results largely support our hypotheses and suggest that the sustained growth path is the ideal mode nascent online sellers should struggle for, since it is significantly positively related to the firm size that the sellers can achieve. To achieve their goal of firm expansion, new online sellers should aggressively pursue opportunities in the short term, which is a reflection of the “the growth of the fitter” principle. Our findings also suggest that E-commerce platforms may attempt to facilitate the sustained growth path of sellers through including growth path analysis in the evaluation system of online stores

Impacts of climate change on TN load and its control in a River Basin with complex pollution sources

It is increasingly recognized that climate change could affect the quality of water through complex natural and anthropogenic mechanisms. Previous studies on climate change and water quality have mostly focused on assessing its impact on pollutant loads from agricultural runoff. A sub-daily SWAT model was developed to simulate the discharge, transport, and transformation of nitrogen from all known anthropogenic sources including industries, municipal sewage treatment plants, concentrated and scattered feedlot operations, rural households, and crop production in the Upper Huai River Basin. This is a highly polluted basin with total nitrogen (TN) concentrations frequently exceeding Class V of the Chinese Surface Water Quality Standard (GB3838-2002). Climate change projections produced by 16 Global Circulation Models (GCMs) under the RCP 4.5 and RCP 8.5 scenarios in the mid (2040–2060) and late (2070–2090) century were used to drive the SWAT model to evaluate the impacts of climate change on both the TN loads and the effectiveness of three water pollution control measures (reducing fertilizer use, constructing vegetative filter strips, and improving septic tank performance) in the basin. SWAT simulation results have indicated that climate change is likely to cause an increase in both monthly average and extreme TN loads in February, May, and November. The projected impact of climate change on TN loads in August is more varied between GCMs. In addition, climate change is projected to have a negative impact on the effectiveness of septic tanks in reducing TN loads, while its impacts on the other two measures are more uncertain. Despite the uncertainty, reducing fertilizer use remains the most effective measure for reducing TN loads under different climate change scenarios. Meanwhile, improving septic tank performance is relatively more effective in reducing annual TN loads, while constructing vegetative filter strips is more effective in reducing annual maximum monthly TN loads

Growth of Outward Propagating Fast-magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe

The solar wind in the inner heliosphere has been observed by Parker Solar Probe (PSP) to exhibit abundant wave activities. The cyclotron wave modes responding to ions or electrons are among the most crucial wave components. However, their origin and evolution in the inner heliosphere close to the Sun remains a mystery. Specifically, it remains unknown whether it is an emitted signal from the solar atmosphere or an eigenmode growing locally in the heliosphere due to plasma instability. To address and resolve this controversy, we must investigate the key quantity of the energy change rate of the wave mode. We develop a new technique to measure the energy change rate of plasma waves, and apply this technique to the wave electromagnetic fields measured by PSP. We provide the wave Poynting flux in the solar wind frame, identify the wave nature to be the outward propagating fast-magnetosonic/whistler wave mode instead of the sunward propagating waves. We provide the first evidence for growth of the fast-magnetosonic/whistler wave mode in the inner heliosphere based on the derived spectra of the real and imaginary parts of the wave frequencies. The energy change rate rises and stays at a positive level in the same wavenumber range as the bumps of the electromagnetic field power spectral densities, clearly manifesting that the observed fast-magnetosonic/whistler waves are locally growing to a large amplitude

McCLS: Certificateless Signature Scheme for Emergency Mobile Wireless Cyber-Physical Systems

Mobile Ad Hoc Network is a self-configurable and self-organizing wireless network of mobile devices without fixed infrastructure support, which makes it a good candidate as underlying communication network for the Cyber-Physical Systems in emergency conditions such as earthquake, flood, and battlefields. In these scenarios, efficient communication schemes with security support are especially desired. Two cryptography approaches, the public key cryptography and the identitybased cryptography, face the costly and complex key management problem and the “key escrow" problem in the real-life deployment. Recently, the certificateless public key cryptography (CL-PKC) was introduced to address these problems in previous approaches. However, the efficiency of the schemes based on CL-PKC is not high and can be improved further. In this paper, we present an improved certificateless signature scheme (McCLS) based on bilinear pairings. First, we theoretically compare the efficiency of McCLS with that of existing certificateless signature schemes (CLS). Second, an empirical study is conducted to compare the traditional AODV with the McCLS scheme based on AODV (McDV) in their efficiency and effectiveness against two most common attacks (i.e. redirection attack and rushing attack). Results from theoretical analysis show that the new McCLS scheme is more efficient than existing CLS solutions, and results from empirical studies show that the McDV is able to resist the two common attacks without causing substantial degradation of the network performance

A Semi-Analytical Models to Investigate Performance of Herringbone Wells

Abstract: For herringbone wells with antisymmetrical and curved laterals, the effects of lateral symmetry and camber on production of herringbone wells are analyzed by semi-analytical model. The effects of laterals with different angles, different number and different spans on production of herringbone wells are analyzed on this base. The results indicate that the contribution of mainbore of production is smaller than symmetrical herringbone well whereas the contribution of laterals of antisymmetrical herringbone well is bigger. The total production of antisymmetrical herringbone well is bigger than that of symmetrical herringbone well. The curved laterals will cause less production comparing with deviated laterals. The bigger the lateral angle is the higher is production of herringbone wells. The contribution of 1/3 lateral end accounts for about 50% of the total lateral contribution. While total length of laterals is the same, the production of well with two laterals on different sides of mainbore is the highest. Besides, laterals should be put as near as possible to the middle mainbore and there is an optimum span existed

Experimental Investigation on Thermal Management of Electric Vehicle Battery Module with Paraffin/Expanded Graphite Composite Phase Change Material

The temperature has to be controlled adequately to maintain the electric vehicles (EVs) within a safety range. Using paraffin as the heat dissipation source to control the temperature rise is developed. And the expanded graphite (EG) is applied to improve the thermal conductivity. In this study, the paraffin and EG composite phase change material (PCM) was prepared and characterized. And then, the composite PCM have been applied in the 42110 LiFePO4 battery module (48 V/10 Ah) for experimental research. Different discharge rate and pulse experiments were carried out at various working conditions, including room temperature (25°C), high temperature (35°C), and low temperature (−20°C). Furthermore, in order to obtain the practical loading test data, a battery pack with the similar specifications by 2S∗2P with PCM-based modules were installed in the EVs for various practical road experiments including the flat ground, 5°, 10°, and 20° slope. Testing results indicated that the PCM cooling system can control the peak temperature under 42°C and balance the maximum temperature difference within 5°C. Even in extreme high-discharge pulse current process, peak temperature can be controlled within 50°C. The aforementioned results exhibit that PCM cooling in battery thermal management has promising advantages over traditional air cooling

The Proteasome Is a Molecular Target of Environmental Toxic Organotins

BACKGROUND: Because of the vital importance of the proteasome pathway, chemicals affecting proteasome activity could disrupt essential cellular processes. Although the toxicity of organotins to both invertebrates and vertebrates is well known, the essential cellular target of organotins has not been well identified. We hypothesize that the proteasome is a molecular target of environmental toxic organotins. OBJECTIVES: Our goal was to test the above hypothesis by investigating whether organotins could inhibit the activity of purified and cellular proteasomes and, if so, the involved molecular mechanisms and downstream, events. RESULTS: We found that some toxic organotins [e.g., triphenyltin (TPT)] can potently and preferentially inhibit the chymotrypsin-like activity of purified 20S proteasomes and human breast cancer cellular 26S proteasomes. Direct binding of tin atoms to cellular proteasomes is responsible for the observed irreversible inhibition. Inhibition of cellular proteasomes by TPT in several human cell lines results in the accumulation of ubiquitinated proteins and natural proteasome target proteins, accompanied by induction of cell death. CONCLUSIONS: The proteasome is one of the molecular targets of environmental toxic organotins in human cells, and proteasome inhibition by organotins contributes to their cellular toxicity