Experimental study of the influence of interior lining distributions on flashover in the enclosure with different ceiling structures

Different distributions of interior linings in an enclosure have been studied to reveal the influence on time to flashover. Two kinds of ceiling structures, flat ceiling and flat ceiling with beams, were used for enclosure. Six full‐scale experiments were performed to investigate the occurrence of flashover in large enclosures. Heat release rate, gas temperature, and surface temperature of the enclosure were measured and analyzed. Experimental results show that time to flashover is extended for enclosure with large surface areas and large doors. Whether lining the interior linings on the ceiling or beams has a significant effect on flashover. Considering that ceiling fires have effect on the progress of the spread of flame on the wall, time to flashover is reduced for the tests that are fitted with the interior linings on the wall of the enclosure. In the enclosure with beams, the direction of spread of flame on the ceiling is changed, resulting in the change of time to flashover. Additionally, the strength of ceiling jets that is affected by the heat release rate of fire source and the area of the interior linings mounted on the fire source influenced region affects flashover. It is observed that flashover occurs when flame fronts are throughout the upper part of the back wall and the flame‐covered area on the back wall exceeds 0.2 times the area of the back wall.     

Derivation of ideal power distribution to minimize the maximum Kernel migration rate for nuclear design of pin-in-block type HTGR

ABSTRACT

Suppressing the kernel migration rates under normal operation condition is quite important from the viewpoint of the fuel integrity for High-Temperature Gas-cooled Reactors. It depends on both the fuel temperature and the fuel temperature gradient. The presence of the ideal axial power distribution to minimize the maximum kernel migration rate allows us to improve the efficiency of design work. Therefore, we propose a new method based on Lagrange multiplier method in consideration of thermohydraulic design in order to obtain the ideal axial power distribution to minimize the maximum kernel migration rate. For one of the existing conceptual designs performed by JAEA, the maximum kernel migration rate for the power distribution to minimize the maximum kernel migration rate proposed in this study is lower by approximately 10% than that for the power distribution as a conventional design target to minimize the maximum fuel temperature.     

Inhibition of Autophagy at Different Stages by ATG5 Knockdown and Chloroquine Supplementation Enhances Consistent Human Disc Cellular Apoptosis and Senescence Induction rather than Extracellular Matrix Catabolism

The intervertebral disc is the largest avascular organ. Autophagy is an important cell survival mechanism by self-digestion and recycling damaged components under stress, primarily nutrient deprivation. Resident cells would utilize autophagy to cope with the harsh disc environment. Our objective was to elucidate the roles of human disc cellular autophagy. In human disc cells, serum deprivation and pro-inflammatory interleukin-1β (IL-1β) stimulation increased autophagy marker microtubule-associated protein 1 light chain 3 (LC3)-II and decreased autophagy substrate p62/sequestosome 1 (p62/SQSTM1), indicating enhanced autophagy. Then, RNA interference (RNAi) of autophagy-related gene 5 (ATG5), essential for autophagy, showed decreases in ATG5 protein (26.8%–27.4%, p < 0.0001), which suppressed early-stage autophagy with decreased LC3-II and increased p62/SQSTM1. Cell viability was maintained by ATG5 RNAi in serum-supplemented media (95.5%, p = 0.28) but reduced in serum-free media (80.4%, p = 0.0013) with IL-1β (69.9%, p = 0.0008). Moreover, ATG5 RNAi accelerated IL-1β-induced changes in apoptosis and senescence. Meanwhile, ATG5 RNAi unaffected IL-1β-induced catabolic matrix metalloproteinase release, down-regulated anabolic gene expression, and mitogen-activated protein kinase pathway activation. Lysosomotropic chloroquine supplementation presented late-stage autophagy inhibition with apoptosis and senescence induction, while catabolic enzyme production was modest. Disc-tissue analysis detected age-related changes in ATG5, LC3-II, and p62/SQSTM1. In summary, autophagy protects against human disc cellular apoptosis and senescence rather than extracellular matrix catabolism.     

非常温原油透射光谱测量及光学物性影响分析

针对高温采油环境传统检测方法无法实现在线检测的问题,设计了恒温实验系统,利用傅里叶变换红外光谱仪IRTracer-100测量了不同温度下原油的透射光谱,基于双厚度法反演出原油的光学常数n和k与热辐射物性参数α和ρ,研究了不同温度对T、n、k、α和ρ的影响。结果表明:在400~4 000 cm^-1波段内,不同温度下原油透射光谱变化趋势相同,且存在726、1 382、1 471、2 849 cm^-1四个吸收峰。在吸收峰处,温度对原油的透射光谱(T)和光学参数影响显著;随着温度的升高,n逐渐减小,温度为70℃,频率为2 849 cm^-1时,n达到最小为1.34。k和α随温度变化规律一致,40℃时,k和α均达到最大,分别为1.65×10^-4和5.93×10²。ρ受温度影响波动较小,在1.42×10^-2~9.05×10^-2内变化。     

MPPT circuit with analog control suitable for solar cars

This paper presents a maximum power point tracking (MPPT) circuit composed of analog circuits suitable for solar cars. The MPPT controller circuit, which consists of analog switches and two op-amps achieved precise MPPT during solar power generation. This MPPT controller circuit was constructed using a small number of CMOS elements, and the circuit of the step-up DC-DC converter achieved a conversion efficiency higher than 98% as well as weight reduction. Eighteen of the proposed MPPT circuits were installed (in serial and in parallel) in a solar car called “2013 Tokai Challenger” at an international competition, and it was shown that it could generate sufficient power supply from solar power.     

Effect of point and planar defects on thermal conductivity of TiO2−x

In this study, we have investigated the effect of planar defect on thermal and electron transport as compared to point defect in the rutile TiO_2?x. Two series of bulk TiO_2?x (2?x = 2.000, 1.992, 1.985, 1.972, and 1.934) samples were prepared using different heat‐treatment procedures to clearly identify the presence of point and planar defects via powder X‐ray diffraction. The charge carrier density and mobility were determined from the Hall effect measurements using the van der Pauw method. The elastic properties of the studied materials such as bulk modulus, shear modulus, Young's modulus, compressibility, and Debye temperature were evaluated from the measured sound velocities, while their thermal conductivities were determined from the thermal diffusivities, heat capacities, and densities measured in the temperature range between 300 and 1073 K. The theoretical calculation based on Klemens‐Callaway model has been performed to analyze the thermal conductivity. As a result, the effect of planar defects on the carrier mobility was almost equivalent to the effect produced by point defects. On the other hand, the presence of planar defects significantly reduced the thermal conductivity of TiO_2?x as compared to point defect due to strong phonon scattering induced by planar defects.     

Hardness of polycrystalline SiO2 coesite

We measured elastic moduli and hardness of polycrystalline SiO₂ coesite. Translucent polycrystalline bulk coesite with a grain size of about 10 micrometers was fabricated at 8 GPa and 1600°C using a Kawai-type multianvil apparatus. The obtained bulk and shear moduli are 94(1) and 60.2(3) GPa, respectively. The resulting Vickers and Knoop hardness values are 10.9(7) and 9.6(4) GPa, respectively, at an indentation load of 4.9 N. Coesite is as hard as other fourfold coordinated silica materials such as quartz and densified silica glasses. The hardness values of coesite and the fourfold coordinated silica materials are about one-third of those of sixfold coordinated silica materials, stishovite, and seifertite, which are the hardest known oxides.     

Experimental determination of solidified lithium disilicate crystal bandgap energy using EELS and XPS

Lithium disilicate (LS2) has been a crucial parent composition for glass-ceramics since the 1950s because of its excellent chemical and physical durability. In addition, a wide range of electrical properties can be obtained by changing the composition and crystallinity. Bandgap energy is one of the critical electrical properties for designing new lithium silicate-based materials. In this study, the bandgap energy of a synthesized LS2 crystal is evaluated using electron energy-loss spectroscopy and X-ray photoelectron spectroscopy. These two techniques unambiguously establish that the bandgap energy of LS2 is 7.7-7.8 eV, which is in the vacuum ultraviolet region. This confirms the insulating nature of the LS2 crystal.     

Reusable robot system for display and disposal tasks at convenience stores based on a SysML model and RT Middleware

Service robots are increasingly being expected to replace human labor; however, in practical settings, these robots have not been fully utilized, partly because the applications that service robots are expected are quite broad. Suitable hardware and software should be developed in order to cope with a wide variety of applications. Ideally, these resources should be developed using common hardware and software platforms are required. Middleware platforms for robotics software, such as ROS and RT Middleware, have already been developed. However, these platforms still face reusability problems due to the inconsistency present in system architectures. Systems are typically assumed to be reused with a given architecture, and if the user-side software architecture is inconsistent with this assumption, the system's reusability suffers. To address this issue, we propose a procedure for optimizing system development using SysML. In this study, our robot system is designed to complete a display disposal tasks in a convenience store; we verify the validity of the robot system using this task. In addition, to verify the reusability of the developed robot system, we employ system functions developed for another task and demonstrate their reuse and operation.