Correlating reaction time and nausea measures with traditional measures of cybersickness

We provoked cybersickness in participants by immersing them in one of two virtual roller coaster rides using a head-mounted display. As simulation technology is often used in training, our main intention was to examine the effect of the experience on their cognitive function. Participant reaction times before and after the experience were measured by averaging their response time to a visual stimulus over a number of trials. We measured a significant reduction in response time before and after the virtual experience. We also examined the changing state of nausea experienced by participants using some simple nausea measures. These included a repeated nausea rating recorded by participants at two-minute intervals. At the completion of the experience, we averaged these ratings to create a standard nausea score. As participants could decide to stop the experience at any time, we also recorded the voluntary duration of the experience. We correlated our measures with two traditional simulator sickness measures, namely the Motion Sickness Susceptibility Questionnaire (MSSQ) and Motion Sickness Assessment Questionnaire (MSAQ). The standard nausea score provided a simple measure of nausea that could be collected at regular intervals with minimal interference to the immersive experience, and was significantly correlated with both the MSSQ and MSAQ scores.     

Effects of temperature and pressure in oxynitridation kinetics on Si(100) with N2O gas

We have investigated oxynitridation of Si(100) surfaces with nitrous oxide (N₂O) gas in a wide range of substrate temperatures (600–1000 °C) and N₂O pressures (10⁻²–10² Pa). The growth rate and atomic composition of the oxynitride layer have been measured by in situ x-ray photoelectron spectroscopy. The surface morphology of the oxynitride layer has been also observed by scanning electron microscopy. The results show that in higher N₂O pressure (>1 Pa) regime, the nitridation reaction is suppressed by the oxide layer, which quickly forms on the surface. On the other hand, in lower pressure (<1 Pa) and higher substrate temperature (>900 °C) regime, the nitridation reaction strongly occurs because of the active oxidation (etching reaction), which causes the surface roughness. It is found by argon-ion-sputtering measurements that the nitride layer locally exists only near the surface at the reduced N₂O pressure. We discuss qualitatively the oxynitridation kinetics and the effective condition for growing the oxynitride layer.     

Measurement of Micro Kinetics of Hydrogenation in Liquid Phase Using Raman Spectroscopy

Hydrogenation of liquid organic hydrogen carriers is usually carried out in liquid phase. To measure the kinetics of this hydrogenation, an experimental setup using in situ Raman spectroscopy for analysis of the reaction mixture is proposed. With this setup it is possible to perform hydrogenation reactions at temperatures of up to 573 K and pressures up to 25 MPa. For validation of the experimental setup the hydrogenation of 1‐octene was measured in liquid phase. The reaction progress can be monitored in detail by Raman spectroscopy. To determine kinetic parameters from the experimental data, two modeling approaches were applied: a classic kinetic model and a thermodynamic kinetic model. The results were compared to literature data.     

Analysis of the carbon anode in carbon conversion cells

We examine further the electrochemical oxidation of carbon in molten carbonate, based on analysis of published research. Ascending and descending branches of voltage hysteresis found in current sweeps of atomically-ordered graphite and of disordered carbon (coal char) are separated by about 0.20–0.25 V and by 0.10–0.15 V for ordered and disordered forms, respectively, over a wide band of current density, 0.03–0.10 A/cm². The higher voltage of the descending branch is in rough agreement with prediction of the Y. Li model for the carbon/carbonate electrode in the same current range, for ordered graphite (L_a = 70–100 nm) and for disordered structures (L_a = 3–5 nm), respectively. We suggest that the amplitude of the hysteresis represents the difference between the overvoltage requirements for 2- and 4 electron net transfer processes, respectively. The 2 e− reaction (C + CO₃²⁻ = CO + CO₂ + 2e⁻) dominates the low current segment (LCS) of our previous analysis, and the more hindered 4e− transfer reaction (C + 2CO₃²⁻ = 3CO₂ + 4e⁻) dominates the high current segment (HCS). The voltage increase separating LCS from HCS is effected by accumulation of CO₂ within small, melt-filled pores to form highly supersaturated solutions of CO₂, which enhance anode voltage by a concentration overpotential of 0.10–0.25 V. Overpotential increases with reaction extent until (1) overall polarization inhibits the interior reaction and shifts CO₂ production to the more accessible exterior surface, or, (2) at a critical concentration (dependent on surface tension and pore diameter) bubbles nucleate and block current flow in the pores. Further support for this picture comes from the often-reported deviation of the gas composition from the CO/CO₂ ratio of the Boudouard equilibrium at atmospheric pressure, as open circuit conditions are approached in an electrochemical cell. Our interpretation accounts for the mole fraction of CO₂ at open circuit being greater than predicted from the Boudouard equilibrium.     

Microstructure and mechanical properties of reaction bonded B4C-SiC composites: The effect of polycarbosilane addition

Reaction bonded B₄C-SiC composites were prepared by infiltrating silicon melt into porous B₄C-SiC green preforms at 1500 °C in vacuum. The porous green preform was obtained from a mixture of polycarbosilane (PCS) and particle size graded B₄C after pre-sintering at 1600 °C. For the first time, PCS was used to adjust the phase composition and microstructure of the reaction bonded boron carbide composites. It is indicated that the addition of PCS and its content has a significant influence on the microstructure as well as the mechanical properties of the subsequent reaction bonded B₄C-SiC composites. For the B₄C-SiC composite with 5 wt% PCS added, a flexural strength of 319±12 MPa, and an elastic modulus of 402±18 GPa can be achieved, which is 23% and 15% higher than those of the composite without PCS addition, respectively. While, with the higher content of PCS addition, the mechanical properties of the composites are decreased drastically due to the large amount of residual Si agglomeration in the composites. The reaction mechanisms as well as their microstructure evolution processes correlated with the mechanical properties of the reaction bonded B₄C-SiC composites are further discussed in our work.     

Infiltration mechanism and factors influencing carbon/carbon–Zr–Ti–C composites prepared by liquid metal infiltration

The effects of fibre architecture, reaction temperature and holding time on the infiltration performance of carbon/carbon (C/C)–Zr–Ti–C composites prepared by liquid metal infiltration were investigated. The results indicated that samples with a chopped-web needled preform and low initial density had a high final density. Increasing the reaction temperatures resulted in a decrease of the final density of samples. Additionally, increasing the initial holding time appeared to obviously result in a high final density, but its effectiveness was not obvious in later observations. An analysis of the infiltration kinetics and mechanisms indicated that the diffusivity of carbon in the carbide, the open-pore sizes and their distribution in C/C composites were the essential characteristics that controlled the height of infiltrating melts.     

An activated-state model for the prediction of solid-phase crystallization growth kinetics in dried lactose particles

Molecular-level understanding of solid-phase crystallization growth kinetics has the potential to improve the fundamental basis for understanding this process. This understanding has been developed here as part of an activated-state model, which accounts for the effects of the moisture content and the temperature on the crystallization rate. Water-induced crystallization (WIC) at different temperatures (15 °C, 25 °C, 40 °C) and a constant relative humidity (75%) environment has been used to analyze the changes in enthalpy, entropy and Gibbs free energy of activation for the solid-phase crystallization of lactose. WIC showed that, at higher temperatures, crystallization commences at lower moisture contents. The enthalpy and Gibbs free energy of activation increased during the crystallization process, which suggested that the binding energy needed for the formation of an activated complex increased as the moisture content decreased, making the formation of the activated complex more difficult. The entropy of activation, on the other hand, decreased with the decrease in the moisture content. From the activated rate equation, the energy of activation has been estimated to be 39 ± 2 kJ mol⁻¹, which is similar to the literature value (40 kJ mol⁻¹) for the solid-phase crystallization of lactose. The reaction rate constant at 25 °C is 1.4 × 10⁻⁴ s⁻¹, which is similar to the literature value of 1.3 × 10⁻⁴ s⁻¹. The WLF equation is inconsistent and hence unreliable in predicting the rates of crystallization at the glass-transition temperature from the analysis of experimental data at different temperatures.     

Microstructural study of hydrogen desorption in 2NaBH4 + MgH2 reactive hydride composite

The desorption mechanism of as-milled 2NaBH₄ + MgH₂ was investigated by volumetric analysis, X-ray diffraction and electron microscopy. Hydrogen desorption was carried out in 0.1 bar hydrogen pressure from room temperature up to 450 °C at a heating rate of 3 °C min⁻¹. Complete dehydrogenation was achieved in two steps releasing 7.84 wt.% hydrogen. Desorption reaction in this system is kinetically restricted and limited by the growth of MgB₂ at the Mg/Na₂B₁₂H₁₂ interface where the intermediate product phases form a barrier to diffusion. During desorption, MgB₂ particles are observed to grow as plates around NaH particles.     

快堆核电厂热力系统加热器设计方案热经济性分析

核电厂热力系统设计需在保证安全性的前提下尽量提高经济性。经济性的影响因素较多，包括技术成熟度、设备成熟度以及系统热经济性等。为了从热经济性的角度确定最优的快堆核电厂热力系统加热器配置，以俄方800 MW钠冷快堆热力系统为参考，基于热平衡分析法建立了适用于快堆核电厂的加热器、立式汽水分离再热器等设备的热力分析模型，进而开发了快堆核电厂热力系统热经济性分析程序，利用俄方设计计算值进行了程序验证。利用新开发的程序研究了不同加热器布置方案、给水焓升分配方案，确定了等焓降分配法的给水焓升分配方案热经济性最好。