C-to-C电子商务的四流合一管理模式探讨

通过对200个C-to-C交易的使用者的调查,对现行C-to-C电子商务中信息流、物流和资金流这三个基本流运行中存在问题的分析,提出了如何运用网络平台更有效地整合三者的设想,并提出为使C-to-C电子商务健康发展,政府的管理流也应是C-to-C电子商务运行中不可缺少的组成成分,提出了用市场模式管理买卖双方的设想和四流合一的C-to-C电子商务管理模式.     

Flow Pattern and Heat Transfer in a Cylindrical Annulus Under 1 g and Low-g Conditions: Experiments

We investigate the thermal convection in an annular cavity, with differentially heated inner and outer cylinders, under the influence of a dielectrophoretic (DEP) force. Applying a temperature gradient to a liquid creates buoyancy driven thermal convection. When additionally a radially acting DEP-force is applied by means of an alternating electric field, the pattern of this convective flow changes which also leads to a change in the heat transfer. Depending on the parameters, e.g. an axisymmetric structure with toroidal vortices appears. Another possible structure are columnar vortices, which extend through the annulus. To isolate the effect of the DEP-force, this experiment is not only conducted in the laboratory, but also in microgravity conditions during parabolic flights. By using DEP-induced convective flows in microgravity a comparable heat transfer as with buoyancy convection under Earth’s condition can be obtained. A better understanding of the heat transport mechanisms inside a dielectric liquid confined between two concentric cylinders can deliver solutions for the improvement of the heat transport in many technical applications.     

Design and Analysis of Storing Experiments: A Case Study

In order to achieve robust and stable food products of desired quality and characteristics, all stages of the food production process, including storage conditions, should be considered during product development projects. This article describes a multistage production development project on low-fat mayonnaise, where experimental design was used to set up a pilot plant study involving ingredient factors, processing factors, and storage factors and their effect on mayonnaise viscosity. The article discusses three alternative empirical modeling approaches to analyze the data—namely, a simple graphics approach, a robustness approach, and a mixed models approach—considering their multistratum (split-plot) structure and repeated measurements of each subsample. In the case study, all information relevant for business decisions was obtained through the combination of graphical analysis and the robustness approach. This information could also be extracted by a practitioner, while the mixed model analysis clearly requires a graduate statistician. In order to obtain valid and useful information for the practitioner in an efficient way, the authors believe that, usually, the first two approaches would be sufficient. The more complex mixed model strategy might be advisable if a deeper understanding is required or desired.     

Diffusivity of hydrogen and methane molecules in A zeolites: Neutron scattering measurements and comparison

The application of neutron scattering to the measurement of intracrystalline diffusivities is reviewed. Experiments on H₂, HD, and CH₄ in A zeolites have shown that the diffusion process is well approximated by jump models. For the smallest molecules (H₂ and HD and NaA), the jumps are isotropically distributed and the jump lengths depend on the molecular mass. For methane in NaA and CaNaA, the jumps are oriented by the framework of the zeolite. The diffusion coefficients show the influence of the molecule size with respect to the window aperture of cavities.     

Recent advances in CKD and ESRD: A literature update

The past year has seen interesting publications in the fields of chronic kidney disease and end stage renal disease. This review highlights some of these important papers and places their findings in the context of clinical care.     

On the Pseudogap State in Y- and La-Type High-Temperature Superconductors: Doping Dependence, Isotope Effects, and Electronic Properties Studied by Neutron Spectroscopy

The doping dependence as well as the oxygen and copper isotope effects on the pseudogap temperature T* were investigated by neutron spectroscopic experiments of the relaxation rate of crystal-field excitations in rare-earth based Y- and La-type high-temperature superconductors. We found three essential results from our truly bulk-sensitive experiments: (1) For all doping levels we had T* > T _c, even in the optimally doped and overdoped regimes. (2) In bilayer high-T _c compounds we observed huge oxygen and copper isotope effects on T*, which give evidence that the pseudogap formation is governed by lattice modes involving both the oxygen and copper ions. In single layer high-T _c compounds, on the other hand, no shift of T* was found for the copper isotope substitution. (3) Our results obtained for all doping levels support the unusual temperature dependence of the gap function in the pseudogap region reported for underdoped Bi-type compounds, i.e., a breakup of the Fermi surface into disconnected arcs in the temperature range T _c < T < T*.     

Recent Progress in Engineering the Atomic and Electronic Structure of Electrocatalysts via Cation Exchange Reactions

In the past few decades, tremendous advances have been made in electrocatalysis due to the rational design of electrocatalysts at the nanoscale level. Further development requires engineering electrocatalysts at the atomic level, which is a grand challenge. Here, the recent advances in cation exchange strategy, which is a powerful tool for fine-tuning atomic structure of electrocatalysts via surface faceting, heteroatom doping, defects formation, and strain modulation, are the main focus. Proper atomic structure engineering effectively adjusts the electronic structure, and thus enhances the electronic conductivity and facilitates the adsorption/desorption of reaction intermediates. By virtue, the cation exchange strategy greatly boosts the intrinsic and apparent activities of electrocatalysts and shows a great potential toward design of new energy conversion devices, such as water splitting devices and metal–air batteries. It is believed that cation exchange offers new insights and opportunities for the rational design of a new generation of electrocatalysts.     

Neutron bombardment of C60 and C70 fullerenes: A spectroscopic and calorimetric study

C₆₀ and C₇₀ fullerenes were neutron-bombarded to an integral dose of 3.28×10¹⁶ n cm^?2. After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C₆₀ insoluble fraction was found at 3.8% while the insoluble fraction of C₇₀ 17.9%. The formation of the CHCl₃ insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C₇₀ appears more sensitive to radiation damage than C₆₀. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630°C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C₇₀ in comparison to C₆₀ at the same neutron dose.     

A Quasi-Elastic and Inelastic Neutron Scattering Study of H2 in Zeolite

The diffusion of molecular hydrogen adsorbed in zeolite 13X at high coverage's has been studied by quasi-elastic neutron scattering for temperatures ranging from 0 to 60 K. No diffusive motion was observed, within instrumental resolution, at temperatures below 20 K, well above the bulk melting point of H ₂ , in contrast to recent NMR studies. The diffusive motion of the adsorbed H ₂ could be described by a liquid like jump diffusion model above 35 K. The diffusion coefficient demonstrates an Arrhenius behavior: D = D₀ exp(E/kT), with D₀ = 1.2 × 10 ^–8 m ² /s and an activation energy of E = 62 K. The inelastic scattering spectrum has also been studied. The scattering consisted of several peaks superimposed on a broad background extending from 1 meV to above 100 meV and is consistent with rotational transitions for a hindered rotor in a strong orientational potential with a broad distribution of barrier heights.     

25th Anniversary Article: The Evolution of Electronic Skin (E‐Skin): A Brief History,Design Considerations,and Recent Progress

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large‐area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large‐area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e‐skin) akin to human skin. E‐skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self‐powering). Continued rapid progress in this area is promising for the development of a fully integrated e‐skin in the near future.     

Neutron scattering as a probe of particle-like excitations in superfluid4He: A model calculation

In the microscopic theory of Bose-condensed liquids, the condensate wave function leads to a coupling of the density fluctuations and the single-particle excitations. A simple parametrized model of this based on coupling weakly damped zero-sound modes with strongly damped free-particle-like excitations Q ²/2m* explains why the phonon-roton resonance inS(Q, ) for superfluid⁴He exists above and belowT but only plays the role of an elementary excitation belowT . It is pointed out that this model also predicts thatS(Q, ) should exhibit a weak, low-frequency peak centered atQ ²/2m*, with weight roughly proportional to the condensate fractionn ₀. As a stimulus to further experimental searches for this branch, some model calculations are given forS(Q, ) forQ1 Å^–1.     

Strategy for Optimizing LC-MS Data Processing in Metabolomics: A Design of Experiments Approach

A strategy for optimizing LC-MS metabolomics data processing is proposed. We applied this strategy on the XCMS open source package written in R on both human and plant biology data. The strategy is a sequential design of experiments (DoE) based on a dilution series from a pooled sample and a measure of correlation between diluted concentrations and integrated peak areas. The reliability index metric, used to define peak quality, simultaneously favors reliable peaks and disfavors unreliable peaks using a weighted ratio between peaks with high and low response linearity. DoE optimization resulted in the case studies in more than 57% improvement in the reliability index compared to the use of the default settings. The proposed strategy can be applied to any other data processing software involving parameters to be tuned, e.g., MZmine 2. It can also be fully automated and used as a module in a complete metabolomics data processing pipeline.     

Finite Step Rate Corrections in Stress Relaxation Experiments: A Comparison of Two Methods

The material response after the application of a constant strain rate ramp, followed, at time t ₁, by a constant strain differs from the response to an ideal (instantaneous) step of strain at short test times. Due to experimental limitations, the ideal step-strain cannot be achieved. As a result, short time stress relaxation data have to be corrected in order to obtain reliable estimates of, for example, the modulus G(t) at times shorter than approximately ten times the ramp time. Here we compare two methods of correction to the stress relaxation data obtained after a linear ramp, assuming a relaxation modulus of the form G(t) =G ₀ e^?(t/τ)^β. The Lee and Knauss correction uses an iterative scheme based on Boltzmann superposition. We compare this method with the Zapas–Craft approach in which the `true' relaxation time becomes t?t ₁/2 (t is the experimental time and t ₁ is the finite time to apply the step in strain). Our numerical computations show that when the relaxation time is short, there is a substantial error in the Lee–Knauss correction. Although the Zapas–Craft approach provides a better correction for times just slightly greater than t ₁/2, it is limited in that it cannot be used for times shorter than t ₁/2. We also investigate the case for which the ramp-step is replaced with a more realistic nonlinear function of time. Finally, it is often desirable to have a similar correction for large deformation responses. The Lee–Knauss method is valid only for linear viscoelastic systems whereas the Zapas–Craft approach has not been rigorously evaluated for large deformations. We evaluate the use of the latter for large deformations within the context of the Bernstein, Kearsley and Zapas single integral model.