Metallographic examination of two medieval knives from Kobilić (Republic of Croatia)

ABSTRACT

Archeological excavation conducted in 2010 in Kobili? (Turopolje region, Zagreb County, Republic of Croatia) yielded two knives from which one shows pattern-welding. This is the first pattern-welded knife reported among Croatian archeological finds. Our knowledge of pattern-welded knife production and trade within medieval Europe is still limited, therefore we decided to carry out a metallographic examination of both knives found at the Kobili? 1 site. Both knives are of excellent functional quality. The pattern-welded knife has a single-patterned core, which ends before reaching the pointed part of the blade, and to which another strip of phosphoric iron was welded from above to increase the overall decorative effect. The overall construction of the pattern-welded knife is fairly typical of such 13th-century pattern-welded blades. The other knife blade is made of one heterogeneous piece of steel, distinguishing it from the majority of contemporary knives. The provenance of the knives remains unknown, but considering that the pattern-welded knife is the only find known from the territory of Croatia to date, it is very likely that is was imported.     

The history of the metallographic study of the Japanese sword

The traditional Japanese Sword (Nihon Token) is an object of great beauty and a marvel of empirical technology. The development of metallography in modern Japan is closely tied to the scientific study of the Japanese Sword, with the first metallographic studies started in 1908 by Kuni-ichi Tawara.     

线性成型装药的威力研究

论文从理论和试验两方面探讨了试验材料和手段对线性成形装药威力测试结果的影响,认为线性装药在射流形成过程中拉伸是二维的,这样射流切割刀容易断裂,威力相对减小;靶板尺寸和起爆方式都能够影响其威力测试结果.提出了在测试线性装药的威力时采用的靶板长和宽一般分别选择其装药长度和宽度的2倍左右为最佳.     

对《建筑设计防火规范》流速法计算模型的理解与分析

对《建筑设计防火规范》（以下简称《建规》）以及有影响的几个文献加压送风流速法中背压系数的取值原则,进行了解读,推导出了背压系数的计算数学模型,并据此作了大量的数值计算。证明背压系数是个由0~1.0的非均匀性增加的＂有上界＂函数。分析表明,《建规》流速法采用以增大系统总风量即乘上背压系数的倒数1/a的方法来解决背压问题,显然值得商榷,因为这样做不仅放过了制造背压的真凶,而且加大的风量并不能保证能分配到我们所需要的关键部位,而造成很大的资源浪费。要解决背压问题,首先要弄清其本质,因为背压产生的根源：在于气流通往无限空间的进程中,串联了一道道门洞（缝）使通路＂当量流通面积＂缩小,阻力增大对该路气流形成的＂气流瓶颈＂所致。特别要指出的是：背压问题本身是把双刃剑,当剑指抵御烟气入侵的有效气流时,应采取有效措施削弱它乃致消除它,当剑指无效气流时,应该极力强化它,使其维我所用。     

一类素的周期整函数

本文的目的是建立如下结论,以致部分地回答了C.C.Yang提出的问题; 对任非偶,级小于1的整函数h(z),周期整函数 F(Z)=cosz·exph(sinz)是素的     

The evaluation of global migration and the assessment of related parameters by a spectrophotometric methodology

In this work, the theory and measurement of migration is discussed in terms of the assessment of the ‘change’ of migration as a function of time. Instead of residue measurement, migration can also be evaluated very quickly and with high accuracy by spectrophotometric means. From these data the maximum possible global migration M_x can be found, which allows one to predict quality behaviour of plastics. Also other effects such as weathering and influences from transport-conditions can be evaluated. It is clear that the proposed testing procedure does not interfere with the conventional weight-procedure. Indeed, the simulant can be removed for residue measurements at any time. The importance of the proposed methodology is the time response wherein assessment can be performed and knowledge of the migrational behaviour of the plastics can be found.     

Influence of aggregate content on the migration coefficient of concrete materials using electrochemical method

In order to investigate the effect of coarse aggregate content on the chloride ion migration coefficient of concrete, specimens with different coarse aggregate volume fractions and two water/cement (w/c) ratios of mortar matrix were used. The chloride ion migration coefficient of concrete is obtained using the electrochemical technique to accelerate chloride ion migration in cement-based material and the experimental results were plotted as a function of the fine aggregate volume fraction. The results are analyzed comparing experimental results and theoretical models that represent the concretes as three-phase composite materials. The three phases are the mortar matrix, the coarse aggregate, and the interfacial transition zone between the two. The chloride ion migration coefficient is used to assess the dilution, tortuosity, interfacial transition zone (ITZ) and, percolation effects of coarse aggregate in concrete. It appears that the dilution and tortuosity effects are a dominant factor affecting the chloride ion migration coefficient of concrete in the low volume fraction of coarse aggregate. As the volume fraction of coarse aggregate increases to 40 and 20% in concrete of w/c ratio 0.35 and 0.45, respectively, the ITZ with percolation effects are significantly.     

Effect of faceting on twin grain boundary motion in zinc

Faceting and migration of incoherent twin grain boundary in Zn [112?0] flat single crystals has been investigated. The stationary shape of the slowly migrating incoherent twin grain boundary of the twin plate tip was studied and migration velocity was measured in situ in the range from 473 K to 692 K using polarized light. Below 623 K the incoherent twin grain boundary represents the facet which forms at a 43° angle to the coherent twin grain boundary. Above 623 K the incoherent twin grain boundary represents the facet, whose position changes from the initial to 75° to the coherent twin grain boundary as temperature increases. Below 623 K the incoherent twin, grain boundary moves at very low experimentally determined activation enthalpy 19.3 kJ/mol of facet migration. Above 623 K the experimentally determined activation enthalpy for the facet migration is 154.4 kJ/mol, which is higher than the activation enthalpy of grain boundary diffusion in Zn. These results clearly indicate that there is a strong effect of the grain boundary shape on the migration velocity of the twin tip. We suppose that there is a grain boundary structural phase transition in this system: facet with high coincidence site lattice transforms to facet with low coincidence site lattice with disordered structure at 623 K.     

Molecular dynamics calculations of properties of the self-interstitials in copper and nickel

Molecular dynamics calculations are performed to study the properties of self-interstitials in copper and nickel using semi-empirical, many-body potentials based on Embedded Atom Method. A set of values of formation, binding and migration energy calculated for single, di-, tri-, tetra-, penta- and hexa-interstitial in copper and nickel are reported. The stable configurations and migration mechanism of them are also presented. The results show that the small interstitial clusters have a significant lower migration energy than the single interstitials and move in the form of one-dimensional crowdion migrations. The clusters in copper are very mobile and the tri-, penta-interstitial in nickel are less mobile because they are difficult to relax to the crowdion dumbbell configurations. The results are also compared with available experimental investigations and previous interstitial calculations using pair potentials.     

Impact assessment of chromite mining on groundwater through simulation modeling study in Sukinda chromite mining area, Orissa, India

The pre-Cambrian chromites ore deposits in Sukinda valley, Jajpur District, Orissa, India, are well known for chromite ore deposits. The exploitation of the ore is carried out through open cast mining method since the last few decades. In the process, the overburden and ore dumps are stored on ground surface, where leaching of chromite and other toxic element takes place particularly during monsoon seasons. This leachate may cause threat to groundwater in the vicinity. An integrated approach has been adopted to evaluate possibility of pollution due to mine seepage and leachate migration on groundwater regime. The approach involves geophysical, hydrogeological, hydro-chemical and aquifer modeling studies. The investigation has the significance as many habitats surround the mining area facing groundwater problems.     

Migration of BHT through airspace in food package systems

In the system composed of a plastic package and a solid food, which are only partially in contact with each other, the migration of the plastic ingredient to the food may take place through the airspace between the package and the food unless the ingredient is non-volatile. This paper describes the migration of an antioxidant BHT(2,6-di-tert-butyl-4-methylphenol) from low-density polyethylene films containing BHT, or from pure BHT crystals used as a source of BHT vapour, to model foods such as casein and granulated sugar. The results obtained:

• i confirmed that the migration of BHT occurs from the film to the food even when they are separated completely by an airspace between them
• ii showed that the amount of migration increases with time and attains a practically constant value after a certain period, but the value and the time vary significantly with the food
• iii found that the BHT concentration in the film remains virtually unchanged at all times in the experiments carried out in this study, because the amount of BHT migration is very small compared with the total amount of BHT contained in the film initially
• iv elucidated the relation between the BHT concentration in the film and the equilibrium amount of BHT migration to the food. This result should be useful for the estimation of the amount of BHT migrating from a polyethylene package to a contained food.

     

Nonlinear behaviors in a pulsed dielectric barrier discharge at atmospheric pressure

In this paper, the temporal nonlinear behaviors of pulsed dielectric barrier discharge in atmospheric helium are studied numerically by a one-dimensional fluid model. The results show that the common single-period pulsed discharge with two current pulses per single voltage pulse can take place over a broad parameter range. The rising and falling times of the voltage pulse can affect the discharge characteristics greatly. When the discharge is ignited by a pulse voltage with long rising and falling times, a single-period pulsed discharge with multiple current peaks can be observed. Under appropriate rising and falling times of the voltage pulse, a stable period-two discharge can occur over wide frequency and voltage ranges. Also this period-two discharge can exhibit different current and voltage characteristics with changing the duty cycle. With other parameters fixed, the pulsed DBD could be driven to chaos through period-doubling route by increasing either the falling time or the frequency of voltage pulse.     

Deficiencies of polypropylene in its use as a food-packaging material — a review

The outstanding chemical and physical qualities of polypropylene (PP) combined with an attractive price have made it one of the protagonists in the food-packaging industry. Like other polymers, however, PP tends to lose some of its constituents to the packed product, by migration, and when submitted to thermal, oxidative or radiation stresses PP starts to degrade. These processes are of concern when food is packed in the plastic, for they can cause PP to impart off-odour and off-taste to the packed product and in the worst case can give rise to toxicity of the food. This paper reviews the work that has been done on these processes and considers the recycling of PP for food-packaging use.     

Monte-Carlo simulation of order–disorder kinetics in 2D and fcc binary alloys

The thermodynamic parameters that drive the atomic migration in 2D and 3D binary alloys are studied using Monte-Carlo simulations. The model is based on a vacancy–atom jump mechanism between nearest neighbour sites, with a constant vacancy concentration, so that only the migration counterpart (E_M) of the total activation energy (E_A=E_M+E_F, where E_F is the vacancy formation energy) is determined. The ordering kinetics are well described by exponential like behaviours with one (respectively two) relaxation time in the 2D (respectively 3D) cases. The temperature dependence of the long relaxation time is an Arrhenius law yielding effective migration energies. Slowing down of the relaxation is observed at the Order–Disorder transitions. In both cases, we observe a linear variation of the effective migration energy with the Order–Disorder critical temperature.     

Evaluating substances used in food contact plastic materials: Importance of the chemical information

In Europe, the substances used for the manufacture of plastic materials intended to come in contact with food have to belong to a positive list. The data requested for assessing these substances are specified by the Scientific Committee for Food (SCF) in the Practical Guide of the European Commission (EC). This review shows how this document contributes to preserving consumer health on the basis of chemical information. Some practical examples are treated to illustrate the approach of the SCF to protect consumer safety.     

高精度转动惯量测量仪分析与设计

文中讨论的扭振法转动惯量测量仪,不需要测量幅值,根据振荡周期就能给出高精度的转动惯量计算结果。介绍了它的工作原理,并且详细分析了测量系统的误差,并给出了相邻周期误差的估计公式。在此基础上提出了两种数据处理方法,方法Ⅰ针对小阻尼比采用对偶时间序列误差相消,直接计算;方法Ⅱ通过计算阻尼比,把阻尼振荡周期转化为无阻尼自振周期进行转动惯量计算,放松了对阻尼比的要求,提高了计算精度。数学仿真结果表明,两种方法对测量误差都不敏感,且均可满足测量误差<±0.5%的要求。     

毫秒电雷管起爆法跳段原因分析

该文通过对毫秒电雷管延期时间的测试结果，分析了引起毫秒电雷管起爆法延期时间误差的主要因素和跳段的主要原因，提出了预防毫秒电雷管微差起爆跳段事故的有效措施。