Strong flame acceleration and detonation limit of hydrogen-oxygen mixture at cryogenic temperature

A series of experiments were carried out in a closed tube at cryogenic temperature (77 K) for hydrogen-oxygen mixtures. Flame propagation speed and overpressure were measured by optical fibers and pressure sensors, respectively. The first and second shock waves were captured in the cryogenic experiments, although the shock waves always precede the flames in all cases indicating the absence of stable detonation. However, strong flame acceleration was observed for all situations, which is consistent with the prediction by expansion ratio and Zeldovich number. Besides, the tube diameter and length are also critical for flame acceleration to supersonic. All the flames in this work accelerate drastically reaching the C-J deflagration state. But at 0.4 atm, only fast flame is formed, while at higher initial pressures, the flame further accelerates to a galloping mode manifesting a near-limit detonation, which could be indicated by the stability parameter χ

Human-computer interaction to human-computer-context interaction : towards a conceptual framework for conducting user studies for shifting interfaces

Computer interfaces have been diversifying: from mobile and wearable technologies to the human body as an interface. Moreover, new sensing possibilities have allowed input to interfaces to go beyond the traditional mouse- and keyboard. This has resulted in a shift from manifest to latent interactions, where interactions between the human and the computer are becoming less visible. Currently, there is no framework available that fully captures the complexity of the multidimensional, multimodal, often latent interactions with these constantly shifting interfaces. In this manuscript, the Hu-man-Computer-Context Interaction (HCCI) framework is proposed. This framework defines 5 relevant interaction levels to be considered during user research in all stages of the new product development process in order to optimize user experience. More specifically, the interaction context is defined in terms of user-object, user-user, user-content, user-platform and user-context interactions. The HCCI framework serves as a concrete tool to use in a new product development process by HCI researchers, design-ers, and developers and aims to be technology independent and future-proof. This framework is a preliminary suggestion to be matched against other innovation devel-opment projects and needs to be further validated

Pneumonia Incidence and Mortality in Mainland China: Systematic Review of Chinese and English Literature, 1985–2008

BACKGROUND: Pneumonia is a leading infectious disease killer worldwide, yet the burden in China is not well understood as much of the data is published in the non-English literature. METHODOLOGY/PRINCIPAL FINDINGS: We systematically reviewed the Chinese- and English-language literature for studies with primary data on pneumonia incidence and mortality in mainland China. Between 1985 and 2008, 37 studies met the inclusion criteria. The quality of the studies was highly variable. For children <5 years, incidence ranged from 0.06-0.27 episodes per person-year and mortality ranged from 184-1,223 deaths per 100,000 population. Overall incidence and mortality were stable or decreased over the study period and were higher in rural compared to urban areas. CONCLUSIONS/SIGNIFICANCE: Pneumonia continues to be a major public health challenge in young children in China, and estimates of pneumonia incidence and mortality vary widely. Reliable surveillance data and new prevention efforts may be needed to achieve and document additional declines, especially in areas with higher incidence and mortality such as rural settings

Spontaneous initiation and development of hydrogen-oxygen detonation with ozone sensitization

This work studies numerically the spontaneous initiation and sustenance of a detonation wave from a hot spot with a nonuniform initial temperature embedded within an H2single bondO2 mixture with and without O3 addition. For the case with either no or just a small amount of O3 addition, a weak reaction wave is auto-ignited at the hot spot, accelerates and then transitions to a pulsating detonation, which propagates along the temperature gradient and quenches as it runs into the cold fresh mixture. However, with increasing O3 addition, the possibility of sustenance of a developing detonation within the gradient is significantly enhanced as it enters the cold mixture. Furthermore, the reduced induction time by O3 addition leads to earlier appearance of the spontaneous reaction wave and detonation formation in the cold mixture, demonstrating that quenching of the detonation is largely related to the instability property of the mixture because the shortened induction time reduces substantially the instability. It is also noted that, for 5%O3 addition, a low-temperature flame produced by the O3 reactions is present in front of the spontaneous reaction wave, inducing a local pressure wave, which facilitates spontaneous initiation and sustains the detonation entering the cold mixture. Moreover, O3 addition renders the critical temperature to induce the minimum spontaneous wave speed higher than the crossover temperature, while they are very close for the case without O3

Simultaneous Target of HEN and Columns with Variable Feed Temperatures for a Toluene Disproportionation Plant

Though toluene disproportionation is an important process for producing <i>para</i>-xylene, it is heavily energy intensive because of its high reaction temperature and the need to separate close boiling-point components. Pinch analysis is often used to target utility requirements for process systems. Nevertheless, the supply and final temperatures of process streams are all predetermined according to the sequential method indicated in the onion model. Therefore, the sequential method ignores the influences of outer level facilities on inner level facilities, which leads to suboptimal solutions. To tackle this problem, variable temperatures of process streams are taken into account in this study to simultaneously target the utility requirements of columns and heat exchanger networks in a toluene disproportionation plant. To this end, relevant equations representing the relationships between feed temperatures and heat duties of columns are first obtained based on simulation data. Second, the equations are integrated into a transshipment model. Meanwhile, variable temperatures are introduced into temperature intervals. As a result, a mixed integer nonlinear programming problem is formulated to minimize the utility requirement in the whole toluene disproportionation plant. Third, the solution results are discussed, providing insights into the optimal results and the sensitivity of utility requirement caused by process streams and separation columns