Experimental and kinetic investigations of the effect of H2/CH4/C2H4 addition on the burning properties of practical jet fuel

Laminar flame speeds of premixed jet fuel/air with the addition of hydrogen, methane and ethylene are measured in a constant-volume bomb at an initial temperature of 420 K, initial pressure of 3 atm, equivalence ratios of 0.6–1.5 and gas mass fractions of 0–50%. The experimental results show that the addition of hydrogen and ethylene can significantly improve the laminar flame speed of the liquid jet fuel, while the addition of methane shows a weak inhibitory effect, and these effects are relatively remarkable on the fuel-rich conditions. The laminar flame speed of the dual fuels/air is linearly dependent on the additional gas mass fraction. A kinetic analysis indicates that the gas addition causes both thermodynamic and chemical kinetic effects on the laminar flame speed of the dual fuels/air. The adiabatic temperature increases and decreases with the addition of hydrogen/ethylene and methane, respectively. A sensitivity analysis shows that the reactions concerning to the H, CH₃ and C₂H₃ radicals become significant with the addition of hydrogen, methane and ethylene, respectively, and that the different values of the rate of product (ROP) of these species via the critical reactions lead to a different promotional or inhibitory effect on the fuel-rich and fuel-lean conditions.     

The performance analysis of a micro-/nanoscaled quantum heat engine

A new model of micro-/nanoscaled heat engines consisting of two thin long tubes with the same length but different sizes of cross section, which are filled up with ideal quantum gases and operated between two heat reservoirs, is put forward. The working fluid of the heat engine cycle goes through four processes, which include two isothermal processes and two isobaric processes with constant longitudinal pressure. General expressions for the power output and efficiency of the cycle are derived, based on the thermodynamic properties of confined ideal quantum gases. The influence of the size effect on the power output and efficiency is discussed. The differences between the heat engines working with the ideal Bose gas and Fermi gas are revealed. The performance of the heat engines operating at weak gas degeneracy and high temperatures is further analyzed. The results obtained are more general and significant than those in the current literature.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定再生锌中铊

铊是一种典型的危险废物,在选冶过程中,再生锌原料中的铊以氧化物或粉尘的形式排放到环境中,严重污染环境并危害人类健康。再生锌成分复杂,若样品消解不完全,直接影响测定结果的准确性。本文比较了微波消解和电热板常压消解对样品的处理效果。结果表明,微波消解法快速环保,但是对于难消解的再生锌样品,因无高氯酸的加入,其氧化性能降低,无法将样品消解完全,导致铊测定结果偏低。而采用高氯酸-硝酸-盐酸-氢氟酸构成的混合酸并于低温加盖聚四氟乙烯盖,进行电热板常压消解,能够有效地解决再生锌样品前处理难题。本实验采用四酸法消解样品,5%盐酸进行浸取,选择Tl 190.794nm为分析谱线,采用电感耦合等离子体原子发射光谱（ICP-AES）法测定再生锌中铊。在仪器设定的最佳测定条件下,当Tl质量浓度为0.10μg/mL~5.00μg/mL时,与发射强度线性关系良好,线性回归方程为y = 180.77x -0.46,相关系数为0.99998。干扰实验表明,在设定的共存离子干扰上限,Pb、Zn、Cu、Fe、Ca、Bi 、Sb、Sn、As、Al、Cd、Si、Ag等对再生锌中铊的测定基本无影响。按照实验方法,对5个不同铊含量水平的再生锌样品进行11次独立测定,其测定范围为ω(Tl):0.0041%~0.21%,方法检出限为0.004μg/mL,实验相对准偏差（RSD）为2.07%~3.11%,加标回收率为97.3%~107.5%。方法简单,操作性强,能够快速准确测定再生锌中铊。     

Complicity of degradable polymers in health-care applications

Polymeric biomaterials have revolutionized biomedical technology and related fields as biomaterials for health-care applications. Recent trend in polymeric medical technology has adapted a tendency to substitute degradable polymers instead of non-degradable synthetic polymers for the advancement of various health-care modalities. They have got considerable attention for their potential in various interdisciplinary arenas, which implies tissue engineering scaffolds, sustainable drug release, delivery agents, regenerative medicine, and development of life-saving devices, implants, dental products as well as in food technology. Various types of degradable polymers are been developed to date having stringent features applicable for various aspects in modern science. Thus, being the most renovative field of biomedicine and biomedical technology degradable polymers has gained substantial acceptance and appreciation recent times. This review critically underlines various degradative polymers and their subtypes, potential applications, types of degradation, and their possible effects in the biological system. Assessment of possible toxicological risks behind is an important criterion to be focused before validating any biomaterial safe for biomedical applications. Therefore various toxicological assessment strategies and their impact in biomedicine and technology were also included. In addition, the risk versus benefit assessment is also critically summarized.     

Thermodynamic optimization of an irreversible regenerative closed Brayton cycle based on thermoeconomic performance criterion

An irreversible regenerative closed Brayton cycle has been optimized using a thermoeconomic objective criterion which is defined as the ratio of net power output to the total cost rate. The total cost rate includes fuel, investment, environmental and operation & maintenance cost rates. In the considered model pressure drops, heat leakages, irreversibilities due to finite-rate heat transfer and internal dissipations have been included. The effects of design parameters, such as isentropic temperature ratio of compressor and turbine, regenerator effectiveness, pressure loss parameter of the cycle, on the general and optimal thermoeconomic performances have been investigated in detail. The results of the study will be helpful for the performance analysis and optimization of practical Brayton heat engine systems.     

Wettability and osteoblast cell response modulation through UV laser processing of nylon 6,6

With an ageing population the demand for cheap, efficient implants is ever increasing. Laser surface treatment offers a unique means of varying biomimetic properties to determine generic parameters to predict cell responses. This paper details how a KrF excimer laser can be employed for both laser-induced patterning and whole area irradiative processing to modulate the wettability characteristics and osteoblast cell response following 24 h and 4 day incubation. Through white light interferometry (WLI) it was found that the surface roughness had considerably increased by up to 1.5 μm for the laser-induced patterned samples and remained somewhat constant at around 0.1 μm for the whole area irradiative processed samples. A sessile drop device determined that the wettability characteristics differed between the surface treatments. For the patterned samples the contact angle, θ, increased by up to 25° which can be attributed to a mixed-state wetting regime. For the whole area irradiative processed samples θ decreased owed to an increase in polar component, γ^P. For all samples θ was a decreasing function of the surface energy. The laser whole area irradiative processed samples gave rise to a distinct correlative trend between the cell response, θ and γ^P. However, no strong relationship was determined for the laser-induced patterned samples due to the mixed-state wetting regime. As a result, owed to the relationships and evidence of cell differentiation one can deduce that laser whole area irradiative processing is an attractive technology for employment within regenerative medicine to meet the demands of an ageing population.     

Finite-size corrections to Poisson approximations in general renewal-success processes

Consider a renewal process, and let K?0 denote the random duration of a typical renewal cycle. Assume that on any renewal cycle, a rare event called “success” can occur. Such successes lend themselves naturally to approximation by Poisson point processes. If each success occurs after a random delay, however, Poisson convergence can be relatively slow, because each success corresponds to a time interval, not a point. If K is an arithmetic variable, a “finite-size correction” (FSC) is known to speed Poisson convergence by providing a second, subdominant term in the appropriate asymptotic expansion. This paper generalizes the FSC from arithmetic K to general K. Genomics applications require this generalization, because they have already heuristically applied the FSC to p-values involving absolutely continuous distributions. The FSC also sharpens certain results in queuing theory, insurance risk, traffic flow, and reliability theory.     

低重复频率激光放大系统中再生腔的结构性能及实验研究

本文从高斯光束的理论出发,充分考虑到放大介质的克尔非线性效应的影响,引入了一个与之相应的非线性传输矩阵,对低重复率的钛宝石激光放大系统中的再生腔的结构性能进行了分析研究。并以此为根据,在实验上设计了激光放大再生腔,实现了TEM_oo模激光振荡,并得到了腔倒空脉冲。     

Understanding root cause of stick–slip vibrations in deep drilling with drag bits

In search for the root cause of stick–slip, a mode of torsional vibrations of a drilling assembly, a linear stability analysis of coupled axial–torsional vibrations has been carried out. It has been shown that in a rotary drilling system with axial and torsional degree of freedom two distinct modes of self-excited vibrations are present: axial and torsional. These axial (torsional) modes of vibrations are due to resonance between the cutting forces acting at the bit and the axial (torsional) natural modes of drillstring vibrations. It has been demonstrated that although axial and torsional modes of vibrations do affect each other the underlying mechanisms driving these modes of vibrations are completely different. In particular, the only driving mechanism of the axial vibrations is the regenerative effect, while there are two distinct mechanisms that drive the torsional vibrations: (i) the cutting action of the bit, and (ii) the wearflat/rock interaction. Moreover, in the case of the torsional vibrations the regenerative effect plays only a secondary role. The results of the present study indicate that the axial compliance can play a stabilizing role. In particular, the stabilizing role of the axial compliance increases as the ratio of the torsional to the axial natural frequency of the drillstring vibrations decreases.     

Cutting process of composite materials: An experimental study

This paper focuses on experimental research of milling process of the epoxide-polymer matrix composite reinforced carbon fibers (EPMC—carbon composite). An influence of two control parameters, namely feed and rotational speed, on cutting forces is investigated. The experiment is conducted on a CNC machine with feed rate ranging from 200 to 720 mm/min and rotational speed from 2000 to 8000 rpm. The experimental time series are analysed by means of the delay coordinates method in order to find stable cutting regions and to recognize the kind of behaviour. Using this information, a new model for the cutting forces is proposed that can be used to build a new regenerative vibration model for EPMC milling.