镍基高温合金中Fe、Mo的联合测定

试样经酸溶解后,用同一母液对镍基高温合金中Fe、Mo进行联合测定。采用EDTA掩蔽干扰元素后直接进行铁量的测定,硫脲作还原剂测定钼量,两元素线性良好。该方法简便快速,已用于实际样品的测定,结果令人满意。     

Rapid growth problems: ascites and skeletal deformities in broilers

Over the last 40 yr, genetic selection for rapid growth and improved feed efficiency has been very effective in meat-type poultry. Combined with changes in the feed that have increased both the nutritional and physical density to encourage a high nutrient intake, growth rate has more than doubled. The effect of genetic selection for high muscle to bone ratio and high calorie intake of a ration that supplies all nutritional requirements causes significant mortality from cardiovascular disease. In the chicken, sudden death syndrome (flip-over) and pulmonary hypertension syndrome resulting in ascites are the most important. Ruptured aorta, spontaneous turkey cardiomyopathy (round heart), and cardiomyopathy causing sudden death produce high mortality in turkeys. Rapid growth induced by high nutrient intake alone can cause severe lameness, bone defects, and deformity, as these problems are seen in animals that have not been selected for rapid growth: dogs, horses, pigs, ratites and wild birds kept in zoologic gardens. In meat-type poultry, growth-related disease can be reduced or eliminated by reducing feed intake without affecting final body weight. Rapid growth alone may not be the pathogenic mechanism that results in cardiovascular or musculoskeletal defects. Metabolic imbalance induced by high nutrient intake may cause some of the conditions. These metabolic problems might be corrected without reducing growth rate.     

Fundamentals of Bubble Formation during Coagulation and Sedimentation Processes

Conventional coagulation and sedimentation processes can be significantly disrupted by gas bubbles, attaching to, and then floating coagulant floc. This study sought to understand the fundamental factors that lead to bubble formation and corresponding floating floc during coagulation and sedimentation. Gas bubbles (causing the floating floc) can form whenever the total dissolved gas pressure exceeds the local solution pressure, which can occur at localized minimum pressures during rapid mixing at high fluid velocities. Very high rate rapid mixers can cause bubble formation and floating floc even in waters undersaturated with dissolved gas. The formation and stability of floating floc are dependent on the local solution pressure, amount and type of dissolved gas supersaturation, temperature, length of rapid mixing, surface chemistry of the mixing paddle, floc, and attachment forces.     

Transition from Crystal to Metallic Glass and Micromechanical Property Change of Fe-B-Si Alloy During Rapid Solidification

Metallurgical and Materials Transactions B - The effects of high undercooling and a large cooling rate can be achieved by the use of a containerless drop tube technique, which is conducive to rapid...     

Elimination of yield point in steel sheets by rapid temperature change

As shown by Koistinen,^1,2 rapid induction heating and quenching can be used to eliminate the yield point and stretcher strains that appear during forming operations on low-carbon steel sheets. Here it is pointed out that such rapid temperature change can produce inhomogeneous plastic deformation, and is then the thermal equivalent of temper rolling or flex-leveling. Theoretical heating (cooling) requirements for eliminating discontinuous yielding on this basis are derived from existing thermoelastic solutions, and experimental results on aged temper-rolled sheet specimens are presented in support of the calculations. The necessary rate of temperature change is more easily reached by quenching than by rapid heating, but rapid heating is essential to control the carbon and nitrogen taken into solution and for high product output. The required rate of temperature change is easily obtainable for sheets of 14 gage (0.19 cm) and heavier, but as sheets become thinner the minimum rate increases rapidly. Because of an increased rate of aging after rapid heating and cooling, the process is of little interest to steel producers as a substitute for temper rolling, but may be attractive to industries which consume large quantities of rimmed steel sheet.     

Orienting grains with{110} surface traces

Analytical equations for cubic crystals are developed relating a grain or crystal surface orientation to the angles between {110} traces on the surface.This allows easy and rapid orientation determinations with a computer with as high an accuracy as the trace data will permit. If the {110} intertrace angles can be ascertained with high precision, then four trace directions will usually suffice to give a unique grain or crystal surface orientation. Otherwise, more than four trace directions may be required.     

Characterization of combinatorial peptide libraries by electrospray ionization Fourier transform mass spectrometry

The advantages of Fourier transform mass spectrometry (FTMS) are precision high mass accuracy measurements and the capability of high resolution, multistage mass spectrometry together with a number of other advanced features. These powerful facilities can be used to rapidly screen complex mixtures without the necessity of chromatographic separations. The example shown here illustrates the use of the high resolving power and accurate mass capabilities of FTMS for the rapid, direct analysis of a complex mixture, which had been ionized by direct infusion electrospray ionization.     

用超快速冷却新工艺生产GCr15轴承钢

 通过对GCr15轴承钢高温终轧后进行冷却速度大于100 ℃/s的超快速冷却试验,研究了轧后不同冷却工艺制度对组织形态和网状碳化物的影响,结果表明,高温终轧后进行超快速冷却可抑制网状碳化物析出,发生伪共析转变而得到细片层间距的珠光体型组织——索氏体,并促进珠光体形核和减小碳原子扩散能力,达到细化晶粒的目的,得到利于球化退火的预备组织。     

基于信息技术的模块化组织变革研究

模块化的企业组织能适应组织流程的快速重组，能够根据市场需求快速配置能力和关系，时刻保持组织的高效率和对客户的优质服务。从信息技术出发，提出了模块化组织结构形式，分析了模块化组织结构的特点，阐述了构造模块化组织应注意的几个问题。     

金属喷射成形的进展

喷射成形是近年来发展极其迅速的一种崭新的金属和合金成形技术 ,它不仅仅具有快速凝固的优点 ,可以生产低偏析、细晶粒、高致密度和近终形尺寸的坯料 ,而且简化了生产工序 ,从而比一般粉末冶金生产工艺降低了成本。本文综述了该工艺在镁基、铝基、铜基、铁基、镍基等合金以及复合材料等不同金属和合金中的研究及应用情况 ,并讨论了它的发展趋势 ,指出该工艺是发展快凝材料的一个重要途径 ,具有广阔的应用前景     

Development of ultrasonic sensor for non-intrusive measurement of temparture in powder materials

Abstract

Fine and ultrafine powders are often used as starting materials for fabrication of advanced materials; they are first formed into desired shapes and then consolidated into high density parts by application of pressure and heat. Electroconsolidation is a densification method for rapid pressure assisted densification of complex shaped parts made from powder preforms. The part to be densified is immersed in a bed of free flowing, electrically conducting, graphite powder medium within a cylindrical die chamber. Pressure is applied externally and heat is generated internally by resistively heating the graphite powder. Because of rapid heating and the attendant wide temperature fluctuations possible with resistive heating, it is of paramount importance to measure and control the temperature in the die to achieve reproducible densification properties. This paper describes an ultrasonic pitch-catch sensor that can be used to non-intrusively measure the temperature of a graphite powder bed. Results of ultrasonic data for heating trials conducted at up to ≈3000°C indicate that the average temperature in a graphite powder bed can be predicted to within 2-3%. The ultrasonic sensor can be used to precisely control the heating trajectory and densification of parts with reproducible properties.     

Rapid trisomy diagnosis (21, 18, and 13) using fluorescent PCR and short tandem repeats: applications for prenatal diagnosis and preimplantation genetic diagnosis

PURPOSE AND METHODS: Prenatal diagnosis of fetal trisomies is usually performed by cytogenetic analysis from amniotic fluid. This requires lengthy laboratory procedures and high costs and is unsuitable for large-scale screening of pregnant women. An alternative method, which is rapid and inexpensive and may potentially be suitable for diagnosing trisomies even from single fetal cells, is the fluorescent polymerase chain reaction (F-PCR) using polymorphic small tandem repeats (STRs). RESULTS: In this paper we present data demonstrating that fluorescent PCR amplification of STRs can be used for rapid diagnosis of trisomy 21, trisomy 18, and trisomy 13 and can be successfully applied to both prenatal diagnosis and diagnosis of single cells. This study also reports significant numbers of prenatal diagnoses using quantitative fluorescent PCR. CONCLUSIONS: We believe that further studies of greater numbers of samples will determine the absolute reliability of this technique. These results also provide a model for trisomy diagnosis from single cells using multiple STR markers for either preimplantation genetic diagnosis or, potentially, diagnosis from fetal cells isolated from maternal blood.     

LA-ICP-MS微区分析及其在金矿床研究中的应用

随着分析技术的飞速发展,从而使地质学研究逐渐由定性描述向数据定量评价转化。但多数地质分析测试技术对某些含量很低或比较特殊的样品分析时仍存在不足或不能满足研究目的;然而,激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)微区分析技术可以实时、快速、高灵敏度、高分辨率及多元素同时测定,并可提供同位素比值信息而使上述问题得以解决。近年来,LAICP-MS分析技术在金矿中的应用,对准确厘定金矿床的成矿时代,探讨成矿物质来源、了解矿床的成矿机制及正确认识矿床的成因等方面具有重要意义。     

铁基合金快淬装置用陶瓷喷嘴的研究

陶瓷喷嘴是制取非晶态金属薄带快淬装置的关键部件之一。铁基合金的快淬工艺要求陶瓷喷嘴在高温下具有化学稳定性、耐冲刷性、抗热震性,且易机械加工。根据喷嘴的材料与工艺的选择试验结果。选用了热压烧结氮化硼(BN)基陶瓷喷嘴。本文叙述了不同材料与工艺制备的喷嘴性能,及使用试验。结果表明,含有氧化物加入物的BN基热压烧结陶瓷喷嘴的各项性能指标,是符合使用要求的。     

Characterization of Flow Behavior of Semi-Solid Slurries with Low Solid Fractions

Semi-solid slurry casting is a metal-forming process that involves transforming liquid metal into slurry having a low solid fraction and then forming the slurry into solid parts. To successfully apply this slurry-forming process, it is necessary to fully understand the flow behavior of semi-solid slurries. This present work applied the rapid quenching method and the modified gravity fluidity casting to investigate the flow behavior, which involves characterizations of the initial solid fraction, fluidity, and microstructure of semi-solid slurries. Three commercial aluminum alloys were used in this study: 383 (Al-Si11Cu), 356 (Al-Si7MgFe), and 7075 (Al-Zn6MgCu) alloys. The results show that the initial solid fractions can be controlled by varying the rheocasting time. The rapid quenching mold can be used to determine the initial solid fractions. In this method, it is important to apply the correcting procedure to account for growth during quenching and to include all the solid phases. Results from the fluidity study of semi-solid slurries show that the fluidity decreases as the initial solid fraction increases. The decrease is relatively rapid near the low end of the initial solid fraction curves, but is quite slow near the high end of the curves. All the three alloys follow this trend. The results also demonstrate that the slurries that contain high solid fractions of up to 30 pct can still flow well. The microstructure characterization results show that the solid particles in the slurries flow uniformly in the channel. A uniform and fine microstructure with limited phase segregation is observed in the slurry cast samples.     

Study on oxygen tension in the eye. I. Comparative study of oxygen electrodes (author''s transl)]

The index of suspicion for accessory atrioventricular conduction pathways must be high in patients with paroxysmal tachycardias in order to avoid overlooking subtle delta waves or short PR intervals. The existence of many different types of accessory AV conduction syndromes can make therapy difficult. Understanding the physiology of each patient's tachycardia can make successful management more rapid, and empiric therapy should not be pursued indefinitely if early drug regimens are unsuccessful. Electrophysiologic study may elucidate the mechanism of the tachycardia and simplify the selection of an ideal drug regimen.     

用二安替吡啉甲烷光度法测定钛矿中二氧化钛

叙述了在盐酸介质中,用抗坏血酸还原铁,以二安替吡啉甲烷作显色剂,水作参比测定钛矿中的二氧化钛。此法适用于二氧化钛含量小于20．00％;操作简便、快速、准确、灵敏度高、选择性好,能满足日常生产快速分析的需要,可代替传统的铝还原一硫酸高铁滴定法。     

Computerized System for the Sintering of Nanoceramics at High Pressures

A computerized system of apparatuses for the sintering at high pressure of nanoceramics based on refractory compounds was developed. It allows for carrying out the sintering process according to a given program with rapid and accurate regulation of the P-T parameters. Information on the sintering process is stored in an internal data base with the possibility of export. The system can also be used as part of a shop local computing network. The properties of nanoceramics based on various refractory compounds produced with use of the system is given.     

Prediction of roll force in skin pass rolling using numerical and artificial neural network methods

A combination of finite element method and neural network methods was used for rapid prediction of the roll force during skin pass rolling of 980DP and 1180CP high strength steels. The FE based commercial package DEFOEM-2D was used to develop a mathematical model of the skin pass rolling operation. Numerical experiments were designed with different process parameters to produce training data for a neural network algorithm. The friction coefficient was considered as an input parameter in the neural network but it was optimised using an iterative method employing an equation that relates the friction coefficient to the rolling force. The load prediction method described in this paper is sufficiently rapid that it can be used in real-time as an adjustment tool for skin pass rolling mills with error within 10% (based on plant data from POSCO).     

The effects of prepulse-blink reflex trial repetition and prepulse change on blink reflex modification at short and long lead intervals

1. Thin slices of the posterior pituitary can be used as a preparation for the study of biophysical mechanisms underlying neuropeptide secretion. Patch-clamp techniques in this preparation have revealed the properties of ion channels that control the excitability of the nerve terminal membrane and have clarified the relation between Ca2+ and exocytosis. 2. Repetitive electrical activity at high frequencies broadens action potentials to allow more Ca2+ entry and thus enhance exocytosis. Action potential broadening results from the inactivation of a voltage-dependent K+ channel. 3. When repetitive electrical activity is sustained, secretion is depressed. This depression can be attributed in part to action potential failure caused by the opening of a Ca(2+)-activated K+ channel. This channel can be modulated by protein kinases, phosphatases, and G-proteins. 4. The inhibitory neurotransmitter GABA activates a GABAA receptor in the nerve terminal membrane. The gating of the associated Cl- channel depolarizes the membrane slightly to inactivate voltage-gated Na+ channels and block action potential propagation. 5. The response of the nerve terminal GABAA receptor is enhanced by neuroactive steroids and this can potentiate the inhibition of neurosecretion by GABA. The action of neurosteroids at this site could play a role in changes in neuropeptide secretion associated with reproductive transitions. 6. Ca2+ channels in the nerve terminal membrane are inactivated by sustained depolarization and by trains of brief pulses. Ca2+ entry promotes Ca2+ channel inactivation during trains by inhibiting the recovery of Ca2+ channels from inactivation. The inactivation of Ca2+ channels can play a role in defining the optimal frequency and train duration for evoking neuropeptide secretion. 7. Measurements of membrane capacitance in peptidergic nerve terminals have revealed rapid exocytosis and endocytosis evoked by Ca2+ entry through voltage-gated Ca2+ channels. Exocytosis is too rapid to account for the delays in neuropeptide secretion evoked by trains of action potentials. Endocytosis sets in rapidly after exocytosis with a time course comparable to that of the rapid endocytosis observed in nerve terminals at rapid synapses. Our results support the finding in rapid synaptic nerve terminals that endocytosis is inhibited by intracellular Ca2+. Multiple pools of vesicles were revealed, and these pools may reflect different stages in the mobilization and release of neuropeptide.