激光间接驱动内爆靶丸的X光诊断

 报道了神光Ⅱ激光聚变实验中内爆燃料靶丸区电子温度、电子密度以及燃料面密度的X光诊断结果。在电子温度诊断中,采用X射线光谱学方法,根据聚变靶丸燃料区的Ar示踪元素的Ly-β线与He-β线的强度比推断出靶丸燃料区电子温度为(950±100) eV;在电子密度诊断中,利用靶丸燃料区Ar元素的He-β线Stark展宽确定聚变靶丸芯部的电子密度为(0.9±0.2)×10²⁴ cm^-3;在燃料区面密度诊断中,利用X光单能照相技术获得了内爆靶丸的燃料面密度为（3.2±0.5） mg/cm²。     

Laser ultrasonic receivers based on organic photorefractive polymer composites

We present two laser ultrasonic receivers based on organic photorefractive polymer composites with 2-[4-bis(2-methoxyethyl)aminobenzylidene]malononitrile (AODCST) or 2-dicyanomethylen-3-cyano-5,5-dimethyl-4-(4′-dihexylaminophenyl)-2,5-dihydrofuran nonlinear optical chromophores. Experimental results show sensitivities of the ultrasonic receivers of ~9.5 × 10^?8 nm (W/Hz)^0.5 for both composites, and a faster response time (~60 ms) for the AODCST-based laser ultrasonic receiver. We show that such LUS detectors are highly suitable for contactless thickness measurements of aluminum, steel sheets and defect detection with an accuracy of 100 μm.     

Spectrometric Studies on the Sonodynamic Damage of Protein in the Presence of Levofloxacin

Taking bovine serum albumin (BSA) as typical molecules, the sonodynamic damage of protein in the presence of Levofloxacin (LVFX) and its mechanism were studied by fluorescence and UV-vis spectra. Various influencing factors such as ultrasonic irradiation time, pH value, ionic strength and solution temperature on the damage of BSA were also discussed. The results showed that ultrasound can enhance the damage of LVFX on BSA. The damage degree of BSA was aggravated with the increase of ultrasonic irradiation time, solution temperature and ionic strength, whereas decreased with the increase of solution pH value. Furthermore, the reactive oxygen species (ROS) in reaction system were studied by oxidation and extraction photometry. Experimental results showed that the amounts of superoxide anion radical (·O₂ ^ˉ) and hydroxyl radical (·OH) were significantly more than that of singlet oxygen (¹O₂) in the presence of LVFX under ultrasonic irradiation.     

Experimental studying of the effect of active area on the performance of passive direct methanol fuel cell

This work experimentally studies the effect of the size and shape of active area on the performance of passive direct methanol fuel cell. The obtained results show that the cell performance strongly depends on the size and shape of active area. Experimental results of this study also demonstrate that the cell performance improves with an increase in the size of active area. Increasing the size of active area also leads to a lower internal resistance, lower OCV, and higher operating temperature. Furthermore, it was found that the smallest active area (4 cm²) produced the longest stable discharging voltage (about 16.5 h). This study also reveals that the square active area has the best performance and the highest power density compared to the rectangular and circular active areas. Finally, the results prove that the place of applying the clamping force is an important parameter that should be considered in the cell design.     

Study on energy attenuation of ultrasonic guided waves going through girth welds

Ultrasonic guided wave is introduced as a new non-destructive long range pipe inspection method. It can be used to inspect pipe which is inaccessible to other conventional NDT methods, and rapid, long distance inspection can be achieved. An investigation of the guided ultrasonic waves traveling along pipe with special geometry characteristics, such as elbow, several girth welds, and some artificial defects is described. In this paper, factors that may cause attenuation of ultrasonic guided waves are discussed and energy attenuation of longitudinal and torsional guided waves is studied on an experimental pipe having seven girth welds. Good agreement has been obtained between the experiments and the predictions. In the end, the detection sensitivity and locating precision of two guided waves, namely longitudinal and torsional, were compared on defects, such as notch, burr and branch.     

An acoustic resonance technique for finding breaks in gas-filled pipes

An acoustic technique for finding breaks in the wall of a gas-filled pipe has been developed, which is applicable in difficult conditions. A complete pipe is checked from one end in a single rapid measurement by exciting the ‘organ pipe’ resonances of the gas column and using the average spacing between overtones as a measure of the length to the first break. The pipe to be tested may contain valves and sharp bends. Holes smaller than 2 mm² can be detected. An application is described in which the technique was combined with tape recording and computer data processing to provide a means of checking the integrity of over 3000 sampling channels inside a nuclear reactor. Despite the variability of temperature and composition of the gas in this application, defects were located to within 0·4 m in pipes 13 m long.     

Influence of fuel and media on membraneless sodium percarbonate fuel cell

This paper reports the media flexibility of membraneless sodium percarbonate fuel cell (MLSPCFC) using acid/alkaline bipolar electrolyte in which the anode is in acidic media while the cathode is in alkaline media, or vice versa. Investigation of the cell operation is conducted by using formic acid as a fuel and sodium percarbonate as an oxidant for the first time under ‘acid–alkaline media’ configurations. The MLSPCFC architecture enables interchangeable operation with different media combinations. The experimental results indicate that operating under acid–alkaline media conditions significantly improves the fuel cell performance compared with all-acidic and all-alkaline conditions. The effects of flow rates and the concentrations of various species at both the anode and cathode on the cell performance are also investigated. It has been demonstrated that the laminar flow-based microfluidic membraneless fuel cell can reach a maximum power density of 25.62 mW cm^?2 with a fuel mixture flow rate of 0.3 mL min^?1 at room temperature.     

Comparison of the measured phase diagrams in the force-temperature plane for the unzipping of two different natural DNA sequences

In this work, we consider the critical force required to unzip two different naturally occurring sequences of double-stranded DNA (dsDNA) at temperatures ranging from 20 ^°C to 50 ^°C, where one of the sequences has a 53% average guanine-cytosine (GC) content and the other has a 40% GC content. We demonstrate that the force required to separate the dsDNA of the 53% GC sequence into single-stranded DNA (ssDNA) is approximately 0.5 pN, or approximately 5% greater than the critical force required to unzip the 40% GC sequence at the same temperature. In the temperature range between 20 and 40 ^°C the measured critical forces correspond reasonably well to predictions based on a simple theoretical homopolymeric model, but at temperatures above 40 ^°C the measured critical forces are much smaller than the predicted forces. The correspondence between theory and experiment is not improved by using Monte Carlo simulations that consider the heteropolymeric nature of the sequences.     

Stiffness matrix and debye temperature of ReO3 from ultrasonic measurements

We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition-metal oxide ReO₃ by ultrasonic pulse propagation. The elastic stiffness constants at 300 K are: C₁₁ = (47.9 ± 1.4) × 10¹¹ dyne/cm²; C₄₄ = (6.1 ± 0.2) × 10¹¹ dyne/cm²; C₁₂ = (?0.7 ± 2.8) × 10¹¹ dyne/cm². These elastic constants indicate a crystal with highly anisotropic shear propagation. The Debye temperature of the compound from these measurements is 528 K. This value is somewhat higher than previous results from specific heat and resistivity determinations.     

H2/Pt/Ce0.9Gd0.1O1.95/Pt/O2 fuel cell operated in the intermediate temperature range 500 – 700°C

Ce_0.9Gd_0.1O_1.95 (GCO), is one of the potential candidate electrolytes for intermediate temperature Solid Oxide Fuel Cells (ITSOFC). GCO has high oxide ion conductivity in the intermediate temperature range (500 – 700 °C) compared to other Ce_1−yGd_yO_2-2/y compositions and the Gd³⁺ ion is the most appropriate dopant material compared to other rare earth materials such as Sm³⁺, Y³⁺, Zr³⁺, etc. Our results show that the fuel cell H₂/Pt/Ce_0.9Gd_0.1O_1.95/Pt/O₂ operated in the temperature range 500 – 700°C gives the maximum power densities 0.0049 W/cm² at 500 °C and 0.0126 W/cm² at 650 °C for cell voltages 0.6275 V and 0.6278 V, respectively, where the electrolyte was kept in 5% H₂ (+ Argon) for 12 hours before use in the fuel cell. Maximum power densities are 0.0038 W/cm² at 500 °C and 0.0270 W/cm² at 650 °C for cell voltages 0.5986 and 0.5913 V, respectively, where the electrolyte was kept in 2 % O₂ (+ Argon) for 12 hours before use in the fuel cell. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Modeling and simulation of planar SOFC to study the electrochemical properties

In this paper, modeling and simulations are carried out using COMSOL Multiphysics. A three-dimensional model is developed for a planar intermediate temperature (IT) solid oxide fuel cell (SOFC). A parametric study has been carried out to analyze the performance of SOFC.Simulations reveal some promising features and enhanced performance of SOFC. It is shown that the maximum value of power (4–3.3) kW/m² still remains higher with significant rise of temperature (600 °C–1000 °C), nearly 0.15 kW/m² is the very small loss of power per 100 °C rise of temperature. Results have shown that the electrolytic current density is (6700–5500) A/m² for peak value of power (4–3.3) kW/m² with increase of temperature (600 °C–1000 °C). For model validation we have plotted a comparison of average current density.     

Q branches in the rotational spectrum of HOC1

We have obtained the far-i.r. rotational spectrm of HOCI from 70–263 cm^?1. The most prominent features of the rotational spectrum are the Q branches, for which we have measured positions. Statistical strengths for the Q branches ave been calculated and μβ, the component of the dipole moment that allows Q branch transitions has been determined from P and R branch line intensities. We find μβ = 1.4 ± 0.2 D. We also calculate Q branch strengths and shifts at stratospheric temperature.     

补偿腔支路对环路热管传热性能影响的实验研究

在环路热管系统工作中,存在因补偿腔温度过高而造成的蒸发器烧干现象。在常规环路热管系统中设计了补偿腔支路,以带走热源向补偿腔传递的径向热量,并对设计的环路热管系统进行实验测试,分析补偿腔支路对环路热管传热特性的影响。实验结果表明:补偿腔支路开启后,在热流密度14 W/cm²时,系统稳定启动所需时间从4 min减少到3 min,表明系统稳定启动所需时间减小,有利于快速启动;在热流密度18 W/cm²下,对应的壁面温度从88.2℃降至85.4℃,系统热阻从0.56 K/W减小到了0.49 K/W,表明系统所能承受的最大热流密度更大,系统热阻也更低,因此系统的传热性能更好。     

风电螺栓轴向应力超声测量标定实验研究

根据超声导波法测量螺栓轴向应力的基本原理,建立了简便有效的声速标定测试实验系统,通过实验分析了测试系统延时误差和温度误差对不同测试方法测量精度的影响.对10.9级42CrMoA风电螺栓轴向应力进行的实际测试表明,超声纵波实际测量误差不大于±2％,纵横波联合测量误差不大于±5％,完全能满足工程应用需求,为该技术在风电领域...     

Ultrasound-homogenization-assisted extraction of polyphenols from coconut mesocarp: Optimization study

Coconut pericarp (shell fiber (mesocarp) and shell (endocarp)), the main by-product of coconut production, is often discarded and causing serious environmental pollution. To make better use of coconut pericarp, the extraction process of polyphenols from coconut mesocarp (CM) carefully studied by screening seven solvent systems, optimizing the assisted ultrasonic process by response surface methodology, and comparing the four processes of Ultrasound-Assisted Extraction (UAE), Homogenization-Assisted Extraction (HAE), Homogenization-Ultrasound-Assisted Extraction (HUAE), and Ultrasound-Homogenization-Assisted Extraction (UHAE). The UAE and HAE are considered to be the main methods for efficient extraction of natural active ingredients. The former effectively destroys the cell wall structure and promotes the intermolecular diffusion based on the cavitation, thermal and mechanical effect of ultrasonic, while the latter breaks the material based on strong shear force between the rotor and stator. Their combinations (HUAE and UHAE) enhance the damage to the cell wall of raw materials and improve the extraction efficiency by the synergistic effect. The results showed that using 60% acetone (V : V) as extraction solvent, solid-liquid ratio of 1:5 g mL⁻¹, ultrasonic temperature of 80 ℃, ultrasonic time of 80 min, ultrasonic power of 225 W, and then homogenizing at 10,000 rpm for 10 min, the total flavonoid content of CM reached the maximum value of 551.99 ± 12.69 mg Rutin g⁻¹ dry weight (dw), while the total phenolic content reached the maximum value of 289.48 ± 4.41 mg GAE g⁻¹ dw at 10,000 rpm for 5 min, which may be related to the oxidative degradation of polyphenols caused by the increase of polyphenol oxidase with the extension of homogenization time. This study provides a technical guarantee for the further utilization of phenolic substances in CM.     

Perborate as novel fuel for enhanced performance of membraneless fuel cells

This paper presents the development of membraneless sodium perborate fuel cell using acid/alkaline electrolyte. In the acid/alkaline electrolyte, perborate works both as an oxidant as well as reductant. Sodium perborate affords hydrogen peroxide in aqueous medium. The cell converts the energy released by H₂O₂ decomposition with H⁺ and OH^? ions into electricity and produces water and oxygen. Such a novel design eliminates the need of a membrane, in which acid and alkaline electrolytes contact with each other. At room temperature, the laminar flow-based microfluidic membraneless fuel cell can reach a maximum power density of 34 mW/cm² with the molar ratio of [Perborate]/[NaOH]?=?1 as fuel and [Perborate]/[H₂SO₄]?=?2 as oxidant. The paper reports for the first time the use of sodium perborate as the oxidant and reductant. The developed fuel cell emits no CO₂, features no proton exchange membrane, inexpensive catalysts, and simple planar structure, which enables high design flexibility and easy integration of the microscale fuel cell into actual microfluidic systems and portable power applications.     

3He melting curve thermometry in a nuclear polarization experiment

Temperature measurement and control are important in brute force polarization experiments. We discuss the installation and use of³He melting curve thermometers in a crystat used to polarize a TiH₂ target. Comparison is made between the melting curve thermometers and the⁶⁰CoCo nuclear orientation thermometer, which is often used in such experiments. The melting curve thermometers provide increased temperature resolution and sensitivity, and were used in a feedback heating system to control temperature to ±5.5 μK at 16.5 mK. The³He melting curve and the⁶⁰CoCo temperature scales are found to agree within 2% at 15 mK. The present status of the melting curve scale and the effect of a magnetic field on melting curve thermometry are also discussed.     

Re-estimation of force constant ratio in the Fe-Ni system

The temperature variation of second order Doppler shift of ⁵⁷Fe embedded as a dilute impurity in Ni host has been calculated by incorporating both the force constant change and the mass change at the site of the impurity. Comparison of the calculations with available measurements of second order Doppler shift gives definite evidence for the change of force constant λ′/λ. It appears that λ′/λ lies in the range 2·1–2·7 around the defect site. The analysis of the data in the high temperature limit further confirms this inference.     

Preparation of graphene/polyaniline-modified carbon nanotubes and their electrochemical properties in microbial fuel cell

Using chemical vapor deposition methods to prepare carbon nanotubes growing in situ on a carbon felt, graphene and polyaniline were applied to the carbon felt for modifying carbon nanotubes. Microbial fuel cell was constructed with graphene/polyaniline-modified carbon nanotubes as anode, graphite as cathode, and glucose solution as substrate. The effects of electrodes, substrate concentration, and temperature on the properties of microbial fuel cell have been studied. At 38 °C using glucose solution of 1450 mg L^?1 and external resistance of 2500 Ω, the optimum output voltage of 687 mV and removal rate of 83% for chemical oxygen demand were obtained in the microbial fuel cell. The prepared nanomaterials are stable and reusable.