Optimum film thickness of thin metallic coatings on silicon substrates for low load sliding applications

The frictional behaviour of thin metallic films on silicon substrates sliding against 52100 steel balls is presented. The motivation of this work is to identify an optimum film thickness that will result in low friction under relatively low loads for various metallic films. Dry sliding friction experiments on silicon substrates with soft metallic coatings (silver, copper, tin and zinc) of various thickness (1–2000 nm) were conducted using a reciprocating pin-on-flat type apparatus under a controlled environment. A thermal vapour deposition technique was used to produce pure and smooth coatings. The morphology of the films was examined using an atomic force microscope, a non-contact optical profilometer and a scanning electron microscope. Following the sliding tests, the sliding tracks were examined by various surface characterization techniques and tools. The results indicate that the frictional characteristics of silicon are improved by coating the surface with a thin metallic film, and furthermore, an optimum film thickness can be identified for silver, copper and zinc coatings. In most cases ploughing marks could be found on the film which suggests that plastic deformation of the film is the dominant mode by which frictional energy dissipation occurred. Based on this observation, the frictional behaviour of thin metallic coatings under low loads is discussed and friction coefficients are correlated with an energy based friction model.     

Characteristics of NOx emission with flue gas dilution in air and fuel sides

Flue gas recirculation (FGR) is a method widely adopted to control NO_x in combustion system. The recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance a much improved reduction in NO_x per unit mass of recirculated gas, as compared to the conventional FGR in air. In the present study, the effect of FGR/FIR methods on NO_x reduction in turbulent swirl flames by using N₂ and CO₂ as diluent gases to simulate flue gases. Results show that CO₂ dilution is more effective in NO reduction because of large temperature drop due to the larger specific heat of CO₂ compared to N₂ and FIR is more effective to reduce NO emission than FGR when the same recirculation ratio of dilution gas is used.     

Sensitivity analysis of anti-resonance frequency for vibration test control of a fixture

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the undertest, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.     

A simple method for the removal of thiols on gold surfaces using an NH4OH-H2O2-H2O solution

The removal behavior of self-assembled monolayers (SAMs) of thiol molecules on a gold substrate by an NH(4)OH-H(2)O(2)-H(2)O solution was studied using attenuated total reflectance infrared spectroscopy (ATR-IR) and atomic force microscopy (AFM). Furthermore, the impact of the concentration of NH(4)OH and H(2)O(2) in the solution and reaction temperature on the SAM removal rate and efficiency was explored. The SAM removal rate and efficiency were significantly influenced by the concentration of NH(4)OH rather than H(2)O(2). The solution containing the 2 : 1 molar ratio of NH(4)OH : H(2)O(2) among three different solutions showed the highest removal rate and efficiency in the removal of 11-mercapto-1-undecanol. The increase in the reaction temperature resulted in the enhancement on the SAM removal rate, but it led to the fast delamination of the gold layer. These results may be useful in the regeneration of sensor surfaces relying on gold/thiol chemistry.     

结构防火保护新技术研究

本文介绍我所近年开展的一项研究“喷射无机纤维防火保护技术研究”的意义、特点和进展情况     

多阶段生成器与时频鉴别器的GAN语音增强算法

传统生成对抗网络的语音增强算法(SEGAN)将时域语音波形作为映射目标, 在低信噪比条件下, 语音时域波形会淹没在噪声中, 导致SEGAN的增强性能会急剧下降, 语音失真现象较为严重. 针对该问题, 提出了一种多阶段的时频域生成对抗网络的语音增强算法(multi-stage-time-frequency SEGAN, MS-TFSEGAN). MS-TFSEGAN采用了多阶段生成器与时频域双鉴别器的模型结构, 不断对映射结果进行完善, 同时捕获时域与频域信息. 另外, 为了进一步提升模型对频域细节信息的学习能力, MS-TFSEGAN在生成器损失函数中引入了频域L1损失. 实验证明, 在低信噪比条件下, MS-TFSEGAN的语音质量和可懂度与SEGAN相比分别提升了约13.32%和8.97%, 作为语音识别前端时在CER上实现了7.3%的相对提升.     

Collecting Duct-Specific CR6-Interacting Factor-1-Deletion Aggravates Renal Inflammation and Fibrosis Induced by Unilateral Ureteral Obstruction

Although inflammation and fibrosis, which are key mechanisms of chronic kidney disease, are associated with mitochondrial damage, little is known about the effects of mitochondrial damage on the collecting duct in renal inflammation and fibrosis. To generate collecting duct-specific mitochondrial injury mouse models, CR6-interacting factor-1 (CRIF1) ^flox/flox mice were bred with Hoxb7-Cre mice. We evaluated the phenotype of these mice. To evaluate the effects on unilateral ureteral obstruction (UUO)-induced renal injury, we divided the mice into the following four groups: a CRIF1^flox/flox (wild-type (WT)) group, a CRIF1^flox/flox-Hob7 Cre (CRIF1-KO) group, a WT-UUO group, and a CRIF1-KO UUO group. We evaluated the blood and urine chemistries, inflammatory and fibrosis markers, light microscopy, and electron microscopy of the kidneys. The inhibition of Crif1 mRNA in mIMCD cells reduced oxygen consumption and membrane potential. No significant differences in blood and urine chemistries were observed between WT and CRIF1-KO mice. In UUO mice, monocyte chemoattractant protein-1 and osteopontin expression, number of F4/80 positive cells, transforming growth factor-β and α-smooth muscle actin staining, and Masson’s trichrome staining were significantly higher in the kidneys of CRIF1-KO mice compared with the kidneys of WT mice. In sham mice, urinary 8-hydroxydeoxyguanosine (8-OHDG) was higher in CRIF1-KO mice than in WT mice. Moreover, CRIF1-KO sham mice had increased 8-OHDG-positive cell recruitment compared with WT-sham mice. CRIF1-KO-UUO kidneys had increased recruitment of 8-OHDG-positive cells compared with WT-UUO kidneys. In conclusion, collecting duct-specific mitochondrial injury increased oxidative stress. Oxidative stress associated with mitochondrial damage may aggravate UUO-induced renal injury.     

Fabrication and installation of KSTAR in-vessel control coils

The in-vessel control coil (IVCC) system, which has been designed for dedication of various active feedback plasma control functions, successfully fabricated and installed in the vacuum vessel of the Korea Superconducting Tokamak Advanced Research (KSTAR). The IVCC system consists of sixteen segmented coils that were independently fabricated outside the vacuum vessel and installed without any inside welding or brazing joints. The segmented coil system has several advantages such as eliminating possibility of cooling water leakage at the welded or brazed joints, simplification in fabrication and installation, and easy repair and maintenance of the coil system. Each segment contains eight oxygen-free high conductive coppers, which are grouped to four pairs, called as sections. Consequently, a segmented coil forms four sections for position control, field error correction (FEC), and resistive wall mode (RWM) control in accordance with electrical connection outside the cryostat. The eight conductors (or four sections) with internal coolant holes were enclosed in a rectangular welded jacket made of stainless steel 316LN and electrically insulated from the conductors by epoxy/glass composite layers. This coil system was commissioned up to 5 kA (30 kA-turns) for 5 s to achieve tentative use for the fast vertical plasma position control in the 2010 campaign of the KSTAR. This paper describes the several remarkable results in the fabrication and installation of the IVCC as well as commissioning results.     

人发、小麦国家标准物质中超痕量稀土元素的NAA定值研究

以放化分离和仪器中子活化分析相结合对已经认证、但稀土元素（REE）含量尚未定值的国家一级标准物质人发（GBW09101）、小麦（GBW08503）中的稀土元素进行了超痕量定值分析,利用单步放化分离流程同时定量分离了稀土元素以及涉及到裂变和γ能谱干扰校正的U和Ba,对含量为0.1～30ng/g的La、Ce、Nd、Sm、Eu、Tb、Yb、Lu等8种稀土元素进行定值分析。并针对比例讨论了ICP-MS和NAA对部分稀土元素进行超痕量分析的优势和劣势。     

Failure diagnosis and recovery based on DES framework

As many industrial systems become more complex, it becomes extremely difficult to diagnose the cause of failures. This paper presents a new failure diagnosis approach based on discrete-event systems (DES) framework. In particular, the approach is a hybrid of event-based and state-based ones leading to a simpler failure diagnoser with supervisory control capability. In our approach, we include the failure recovery events for failures in the system model in order to derive a diagnoser we refer to as a recoverable diagnoser. Further, in order to reduce the state size of the recoverable diagnoser, a procedure to construct a high-level diagnoser is presented. The design procedure for diagnoser is presented along with a pump-valve system as a illustrative example.