激光切割技术在钣金加工中的应用研究

在钣金加工中,激光切割技术比传统方法有着优势。激光切割技术在钣金加工中的应用研究,针对了激光切割技术在钣金加工中的各类应用方法,激光切割技术帮助了对于钣金模具的生产环节中模具的生产,而在钣金的薄板切割过程中应用激光切割技术提高了产品质量,缩短了加工周期,并对与传统的机械切割方法与激光切割方法进行了对比实验分析,激光切割在切割精度上优于传统的机械切割方法。     

在普通立式铣床上加工大导程蜗杆的实践

本文介绍了大导程蜗杆在应用中的广泛性。并分析了其传统加工方法的局限性，介绍了在普通立式铣床上加工大导程蜗杆的加工方法。     

高强度粉末冶金锥齿轮加工方法探讨

本文针对粉末冶金锥齿轮应用中强度方面的要求,通过对原料成分、产品形状结构、加工工艺等方面进行分析,得出了高强度锥齿轮加工方法,为高强度粉末冶金锥齿轮加工提供了方法指导。     

巧用华中系统复合循环G71指令车削零件

结合实例详解了华中数控系统复合循环指令G71在实际编程与加工中的应用。此指令的应用,解决了在加工轴类零件过程中运用传统的加工方法难以满足形状复杂、精度高等要求的问题,从而提高了工作效率。     

难加工材料加工方法的现状与发展趋势

有一些材料具有难加工的特点,但是难加工材料往往具有很多优良性能,在很多方面都有着较为重要的应用,例如,钛合金在航空航天工业中的应用,所以对难加工材料的加工方法的研究十分重要。本文就通过对难加工材料加工方法的现状分析,从难加工材料的机械特性、磨削特点以及难加工材料的加工效率低、刀具寿命短等方面进行研究,提出难加工材料的加工方法与未来的发展趋势。     

钼与钼合金的应用及其加工方法

介绍了钼与钼合金的应用及其加工方法。     

钢材力学性能检验用拉伸试样加工宏程序的开发与应用

分析拉伸试样加工方法,提取数控加工参变量进行宏程序开发。经现场应用,较好地解决了不同规格系列拉伸试样需编制不同数控程序的问题,对提高试样加工质量、缩短加工周期等具有重要的实际意义。     

齿科钛及钛合金加工现状

钛具有质地轻、比强度高、生物相容性和耐腐蚀性好等优点,在齿科获得了广泛的应用(表1)。钛是较难加工的金属,经过10多年的努力,齿科加工钛及钛合金的技术有了明显的发展。目前已投入临床应用的加工方法有切削、拉丝、超     

干切削加工技术的发展及应用

解决切削液带来的环境及经济效应的根本方法就是干切削加工技术。本文论述了干切削加工的特点、实施可靠性。并给出了某些应用实例。     

锌精馏碳化硅塔盘加工技术的发展

简要介绍碳化硅制品特性及在精馏塔中应用 ,对手工加工的斜口塔盘和机械加工的平口塔盘两种塔盘加工方法进行比较 ,同时 ,对铣磨床加工平口塔盘进行了一系列完善     

Site Characterization Model Using Artificial Neural Network and Kriging

In this paper, the problem of site characterization is treated as a task of function approximation of the large existing data from standard penetration tests (SPTs) in three-dimensional subsurface of Bangalore, India. More than 2,700 field SPT values (N) has been collected from 766 boreholes spread over an area of 220-km2 area in Bangalore, India. To get N corrected value (Nc), N values have been corrected for different parameters such as overburden stress, size of borehole, type of sampler, length of connected rod. In three-dimensional analysis, the function Nc = Nc(X,Y,Z), where X, Y, and Z are the coordinates of a point corresponds to Nc value, is to be approximated with which Nc value at any half-space point in Bangalore, India can be determined. An attempt has been made to develop artificial neural network (ANN) model using multilayer perceptrons that are trained with Levenberg-Marquardt back-propagation algorithm. Also, a geostatistical model based on ordinary kriging technique has been adopted. The knowledge of the semivariogram of the Nc values is used in the ordinary kriging method to predict the Nc values at any point in the subsurface of Bangalore, India where field measurements are not available. The results obtained show that ANN model is fairly accurate in predicting Nc values. In case of ordinary kriging, a new type of cross-validation analysis shows that it is a robust model for prediction of Nc values. A comparison between the ANN and geostatistical model demonstrates that the ANN model is superior to Geostatistical model in predicting Nc values in the subsurface of Bangalore, India.     

Brain–behavior correlations: Relationships between mother–stranger face processing and infants' behavioral responses to a separation from mother.

Event-related potentials (ERPs) were recorded from 6-month-olds (N = 30) as they looked at pictures of their mother's face and a stranger's face. Negative component (Nc) and P400 component responses from the ERP portion of the study were correlated with behavioral responses of the infants during a separation from their mothers. We measured the mother-directed infant behaviors of distress and visual search for mother during separation in order to determine if they were predictive of infants' brain responses to pictures of the mother's face versus a stranger's face. These behavioral measures are important because they likely reflect the functioning of the emerging mother–child relationship and inform debates about interactions between social experience and face processing. Infant distress and visual search for mother during separation were predictive of face processing ERPs, and this relationship differed across mother and stranger face presentations. In particular, distress was associated with larger amplitude P400 and Nc responses to the mother's face, and visual search for mother was associated with longer P400 and Nc latencies to the stranger's face. Implications for the developing mother–child relationship and face processing system are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain activity differentiates face and object processing in 6-month-old infants.

Event-related potentials were used to determine whether infants, like adults, show differences in spatial and temporal characteristics of brain activation during face and object recognition. Three aspects of visual processing were identified: (a) differentiation of face vs. object (P400 at occipital electrode was shorter latency for faces), (b) recognition of familiar identity (Nc, or negative component, at frontotemporal electrodes [FTEs] was of larger amplitude for familiar stimuli), and (c) encoding novelty (slow wave at FTEs was larger for unfamiliar stimuli). The topography of the Nc was influenced by category type: Effects of familiarity were limited to the midline and right anterior temporal electrodes for faces but extended to all temporal electrodes for objects. Results show that infants' experience with specific examples within categories and their general category knowledge influence the neural correlates of visual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related brain potentials during an extended visual recognition memory task depict delayed development of cerebral inhibitory processes among 6-month-old infants with Down syndrome

Development of cerebral inhibitory processes among individuals with Down syndrome (DS) may be delayed at an early age. In support of this hypothesis, sensory-evoked potentials (EPs) and event-related brain potentials (ERPs) have previously delineated altered habituation to stimuli among infants with DS. The purpose of the current study was to provide extended experience with visual stimuli among 6-month-old infants with and without DS (nDS) to determine if altered ERP and behavioral response decrements would be evident even after repeated presentations of stimuli. An 80/20% oddball paradigm was employed. Infants with DS and nDS were matched according to age and gender. Infants with DS demonstrated significantly larger Nc areas, Nc peak amplitudes, Nc2 areas and, inversely, significantly smaller peak Pb amplitudes when compared to infants nDS. Contrasts of the two study groups were most robust within ERP measures from frontal (Fz) and parietal (Pz) recording sites. Infants with DS also demonstrated a significantly slower decrement of most ERP components with repetitive stimulus experience. Most noteworthy was the observation of little or no decrement of ERP components at Fz among infants with DS. Both infants with DS and nDS demonstrated significantly larger Nc peak amplitudes, Nc areas, Nc2 areas, Pb peak amplitudes and NSW areas to rare stimuli. While significant probability and experiential trends were observed in visual fixation measures across both study groups, there were no significant differences of visual attention between infants with DS or nDS. These data demonstrate the value of ERPs within the study of atypical cognitive development during infancy and support the concept of altered inhibitory processes in the brain of infants with DS.     

Topical application of synthetic pyrethroids to cattle as a source of persistent environmental contamination

Norepinephrine (NE) is one of the most potent positive inotropic drugs available for the treatment of low-output state following open-heart surgery. However, its inotropic effect is often masked by a significant increase of peripheral vascular resistance due to marked vasoconstriction. The purpose of the present study was to investigate whether the use of nicardipine (Nc) and phentolamine (Ph) in combination with NE could ameliorate the adverse vasoconstrictive action of NE. A low-output-state (LOS) model was produced by global myocardial ischemia due to electrically induced intermittent ventricular fibrillations in open-chest dogs. Twenty-eight dogs were divided into 6 groups according to the drugs infused after producing LOS. In the control group, hemodynamic changes similar to the clinical low-output state were observed, e.g., a decrease in cardiac output (CO) and left ventricular dp/dt, and an increase in the systemic vascular resistance (SVR). The use of NE alone produced marked increases in the systemic arterial pressure (SAP), heart rate, and SVR, with a slight increase in CO. The infusion of Nc alone produced decreases in SVR and SAP with a slight increase in CO. The concomitant infusion of NE and Nc produced increases in SV and CO, and decreases in SAP and SVR. The infusion of Ph alone produced no significant hemodynamic changes. The combined use of NE and Ph produced increases in CO, SAP and heart rate, but not to a significant extent. These results suggest that there are major advantages in the concomitant use of NE and Nc for the control of LOS.     

Familiarization, Attention, and Recognition Memory in Infancy: An Event-Related Potential and Cortical Source Localization Study.

This study investigated the effects of familiarization and attention on event-related potential (ERP) correlates of recognition memory in infants. Infants 4.5, 6, or 7.5 months of age were either familiarized with 2 stimuli that were used during later testing or presented 2 stimuli that were not used later. Then, infants were presented with a recording of Sesame Street to elicit attention or inattention and presented with familiar and novel stimuli. A negative ERP component over the frontal and central electrodes (Nc) was larger in the preexposure familiarization group for novel- than for familiar-stimulus presentations, whereas the Nc did not differ for the group not receiving a familiarization exposure. Spatial independent components analysis of the electroencephelogram and "equivalent current dipole" analysis were used to examine putative cortical sources of the ERP components. The cortical source of Nc was located in areas of prefrontal cortex and anterior cingulate cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus probability and event-related potentials of the brain in 6-month-old human infants: a parametric study

The effects of a priori stimulus probability and local-stimulus sequences on the Nc, NSW and Pc components of the event-related brain potentials were studied in six groups of 6-month-old human infants. Predictions from memory, expectancy and attentional accounts of the Nc, NSW and Pc components were examined using an infant-control oddball paradigm in which visual stimuli were presented across groups, at 0.90/0.10, 0.80/0.20, 0.70/0.30, 0.60/0.40, 0.50/0.50 (alternation) and 0.50/0.50 (random) probabilities. The main results indicated that stimulus probabilities and local-stimulus sequences affected Nc amplitude and latency, NSW amplitude but not the Pc component. Concurrent visual fixation performance was also found to be influenced by stimulus probabilities. The results were discussed in terms of the predictions from memory, expectancy and attentional accounts of the infant late components.     

拜耳法流程中碳酸钠升高的原因分析及降低措施

由于铝土矿中钙、镁化合物在溶出过程中形成碳酸碱以及铝酸钠溶液吸收空气中CO2形成碳酸钠等原因,导致流程中碳酸钠浓度升高、溶出率低、蒸发器能耗升高等不利影响。通过抑制反苛化反应、强化结晶析盐、采用机械搅拌以及将拜耳法精液与烧结法精液合流碳分等措施,减少了流程中Nc的循环累积,蒸发母液中Nc浓度由46.59g/L降为30.57g/L。     

Midlatency auditory evoked potentials as indicators of perceptual processing during general anaesthesia

We tested the hypothesis that midlatency auditory evoked potentials (MLAEP) can predict the occurrence of long latency AEP components (LLAEP), which are taken as evidence for perceptual processing. Forty-one patients undergoing cardiac surgery were anaesthetized with propofol and alfentanil. During several periods of surgery we recorded LLAEP. Peak-to-peak amplitude measures were used to determine if a particular LLAEP recording trace contained a recognizable waveform. Both before and after each LLAEP recording epoch, MLAEP and the spontaneous electroencephalogram (EEG) were recorded. Peak latencies and amplitudes of brainstem peak V and midlatency peaks Na, Pa, Nb, Pb and Nc, characteristic frequencies from the spontaneous EEG, mean arterial pressure (MAP) and nasopharyngeal temperature (7) were compared between recording epochs with and without clear LLAEP waveforms. These variables were also used in a discriminant analysis to predict the occurrence of an LLAEP waveform. Pa and Nb latencies were significantly shorter both before and after recording epochs in which an LLAEP waveform occurred, compared with epochs in which no LLAEP waveform occurred. Using a combination of up to six EEG, MLAEP, MAP and T measures, it was possible to predict the occurrence or absence of an LLAEP waveform with a sensitivity of 89% and specificity of 86%. We conclude that MLAEP components provide information on the possibility of perceptual processing during general anaesthesia, and thus may be relevant for monitoring depth of anaesthesia.     

Early adverse experiences and the neurobiology of facial emotion processing.

To examine the neurobiological consequences of early institutionalization, the authors recorded event-related potentials (ERPs) from 3 groups of Romanian children--currently institutionalized, previously institutionalized but randomly assigned to foster care, and family-reared children--in response to pictures of happy, angry, fearful, and sad facial expressions of emotion. At 3 assessments (baseline, 30 months, and 42 months), institutionalized children showed markedly smaller amplitudes and longer latencies for the occipital components P1, N170, and P400 compared to family-reared children. By 42 months, ERP amplitudes and latencies of children placed in foster care were intermediate between the institutionalized and family-reared children, suggesting that foster care may be partially effective in ameliorating adverse neural changes caused by institutionalization. The age at which children were placed into foster care was unrelated to their ERP outcomes at 42 months. Facial emotion processing was similar in all 3 groups of children; specifically, fearful faces elicited larger amplitude and longer latency responses than happy faces for the frontocentral components P250 and Nc. These results have important implications for understanding of the role that experience plays in shaping the developing brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)