带锥面阶梯轴零件加工工艺分析及图解

针对带锥面阶梯轴零件的加工工艺分析,制订其加工工序,并以单步走刀的方式进行零件的加工。从毛坯到零件,每个工步都附加图示,能够提高初学者对数控加工的工艺、工步、工序等理论知识的理解。     

The role of visual working memory in attentive tracking of unique objects.

When tracking moving objects in space humans usually attend to the objects’ spatial locations and update this information over time. To what extent do surface features assist attentive tracking? In this study we asked participants to track identical or uniquely colored objects. Tracking was enhanced when objects were unique in color. The benefit was greater when the distance between distractors and targets was smaller, but was eliminated when the objects changed colors 1 to 4 times per second, even though at any instant they were always uniquely colored. In addition, tracking uniquely colored objects impaired a secondary color-memory task more than tracking identical objects, and holding several colors in working memory eliminated the advantage of tracking uniquely colored objects. Contrary to previous studies showing that feature information is poorly retained during tracking, these findings indicate that surface properties are stored in visual working memory to facilitate tracking performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of lexical processing in a nonnative language.

In three experiments, native Cantonese speakers were asked to read words aloud, name pictures, and translate words. In the study, subjects with different degrees of proficiency in their nonnative language were used (i.e., proficient subjects, adult beginners, and second- and fourth-grade child beginners). The results show that all subjects were more efficient in reading words than in naming pictures when responding in their native language. When the response was in the nonnative language, the proficient subjects were equally efficient in both translating and picture-naming tasks. For the adult beginners, however, translating was faster than picture naming, whereas naming was faster than translating for the child beginners. These results were consistent with the idea that proficient subjects could directly access the meanings of words in the nonnative language, whereas beginners tended to use either corresponding words in the native language (i.e., the adult beginners) or pictorial representations (i.e., the child beginners) as media for such end. These results thus suggest that the proficiency of the nonnative language and the age or method of acquisition of the language are important determinants for the pattern of lexical processing in the nonnative language. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time course of consolidation in visual working memory.

How long does it take to form a durable representation in visual working memory? Several theorists have proposed that this consolidation process is very slow. Here, we measured the time course of consolidation. Observers performed a change-detection task for colored squares, and shortly after the presentation of the first array, pattern masks were presented at the locations of each of the colored squares to disrupt representations that had not yet been consolidated. Performance on the memory task was impaired when the delay between the colored squares and the masks was short, and this effect became larger when the number of colored squares was increased. The rate of consolidation was approximately 50 ms per item, which is considerably faster than previous proposals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

X射线荧光光谱熔片分析的校准曲线与玻璃片质量校正

在铁合金和铁矿石的X射线荧光光谱(XRF)熔片分析中,存在着样品直接灼烧和熔融质量变化不同产生的误差,常用的稀释比校正无法校正这种误差。实验提出在固定质量(体积)的熔剂中熔入系列被测组分的氧化物制备出质量(体积)相同的玻璃片标准系列,建立X射线荧光强度与玻璃片中被测组分体积浓度的函数曲线,使用样品玻璃片质量与校准曲线玻璃片的质量比校准分析结果,即质量校正代替稀释比校正。以纯物质(SiO₂、CaCO₃、Al₂O₃和Fe₂O₃)为标准,用选定的仪器工作条件,建立了硅钙合金分析用Si、Ca、Fe、Al质量分数对荧光强度的校准曲线,其线性相关系数分别为0.9990、0.9993、0.9994、0.9995。用标准样品考察了校准曲线的准确度。t检验结果表明,当玻璃片的质量变化较大时,不使用质量校正测量结果偏差较大,正确度差。     

Working memory is related to perceptual processing: A case from color perception.

We explored the relation between individual differences in working memory (WM) and color constancy, the phenomenon of color perception that allows us to perceive the color of an object as relatively stable under changes in illumination. Successive color constancy (measured by first viewing a colored surface under a particular illumination and later recalling it under a new illumination) was better for higher WM individuals than for lower WM individuals. Moreover, the magnitude of this WM difference depended on how much contextual information was available in the scene, which typically improves color constancy. By contrast, simple color memory, measured by viewing and recalling a colored surface under the same illumination, showed no significant relation to WM. This study reveals a relation between WM and a low-level perceptual process not previously thought to operate within the confines of attentional control, and it provides a first account of the individual differences in color constancy known about for decades. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Modifications of the paraspinous muscle flap: anatomy and clinical application

Soft-tissue defects of the back, particularly involving the paravertebral tissues, are generally covered with myocutaneous, muscle, or fasciocutaneous flaps. The case of a 64-year-old man with a paravertebral malignant fibrous histiocytoma is reported. To ensure adequately radical margins, the ipsilateral trapezius and latissimus dorsi muscles as well as the costal periosteum and the spinous processes were resected between T9 and T12. The resulting defect was covered with a pedicled latissimus dorsi flap and an island flap of the paravertebral muscles. Prompted by this case, we studied the blood supply of the paravertebral muscles in 10 cadavers. The vasculature was visualized after flushing with colored latex and microsurgical dissection. Another 4 specimens were subjected to angiography and tomography. In the majority of cases (8 of 10), three perforators emerging from the intercostal arteries were identified. These were found to communicate in a longitudinal and vertical direction. Before piercing the fascia, they ramified in three layers matching the layers of the paravertebral muscles. Since the intercostal arteries were shown to communicate through anastomoses of adequate caliber, the paravertebral muscles appear to be useful candidates for proximally or distally pedicled transposition or island flaps.     

Respiratory and circulatory parameters of African elephants (Loxodonta africana) anaesthetised with etorphine and azaperone

We compared ischemia reperfusion injury-associated vasospasm and perfused capillary density (PCD) at the microcirculatory level between clamp ischemia and microsurgical ischemia in rat skeletal muscle. Rat cremaster muscle was prepared as an island flap, attached only with pudic-epigastric vessels branching from external iliac vessels. Two types of ischemia, with clamping only or with microvascular anastomosis, were applied at the external iliac vessels for 2 hours followed by 1-hour reperfusion before in vivo microscopic examination for hemodynamic changes. At the end of observation, small segments of the vessels at the clamping site and microsurgical anastomoses site were also harvested for histological examination. It was found that the first- and second-order arterioles had about 12-15% diameter reductions in both groups, whereas diameter reductions of the third-order arterioles were up to 37.8% in the microsurgical ischemia group, much greater than that in the clamp ischemia group (2.3%). There was also no significant difference in PCD reduction between the two groups, although the red blood cell velocity was much slower in the microsurgical ischemia group. Histological examination of the anastomosis site showed massive accumulation of polymorphonuclear neutrophils on the venous endothelium. These results suggested a different degree of endothelial damage and local leukocyte activation between microsurgical ischemia and clamp ischemia. Therefore, we conclude that clamp ischemia cannot replace microsurgical ischemia for studying microcirculatory changes in free tissue transfer.     

Dexter: a device for the assessment of microsurgical instrumentation and instruction of trainees

We present an easily constructed devise, which allows the testing and comparison of microsurgical apparatus, providing a numerical result for statistical analysis. It also enables the trainee microsurgeon to practise basic microsurgical skills in a safe environment. Construction and uses are discussed.     

Usefulness of microsurgery to isolation of recurrent laryngeal nerve and parathyroid during thyroidectomy operations

The authors report their experience of the application of microsurgical techniques in total and subtotal thyroidectomy operations from January 1984-January 1997. Four hundred and eighty-six patients with thyroid diseases were operated upon with both traditional and microsurgical techniques. The comparison of results shows that microsurgical skills are effective in reducing the dangers and important complications in both laryngeal nerves and parathyroids.     

Overcoming spontaneous patterns of coordination during the acquisition of a complex balancing task.

The goal of our study was to analyze the spontaneous coordination of beginners (aged 21-27 yrs) and its development in a complex balancing task on a stabilometer. The emergence of two strategies used in mastering the multiple and redundant degrees of freedom when learning a motor task are examined. Our results showed that beginners were characterized by strong couplings between the joints of the lower limbs. During learning, new and more task-specific couplings emerged that reflected a new organization of the trunk and a decoupling of some joints of the lower limbs that were initially coupled during the first few trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early, Involuntary Top-Down Guidance of Attention From Working Memory.

Four experiments explored the interrelations between working memory, attention, and eye movements. Observers had to identify a tilted line amongst vertical distractors. Each line was surrounded by a colored shape that could be precued by a matching item held in memory. Relative to a neutral baseline, in which no shapes matched the memory item, search was more efficient when the memory cue matched the shape containing the target, and it was less efficient when the cued stimulus contained a distractor. Cuing affected the shortest reaction times and the first saccade in search. The effect occurred even when the memory cue was always invalid but not when the cue did not have to be held in memory. There was also no evidence for priming effects between consecutive trials. The results suggest that there can be early, involuntary top-down directing of attention to a stimulus matching the contents of working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Limited period of action of testosterone on memory formation in the chick.

Domestic chicks will normally peck readily at small colored beads. However, a peck at a bead with an unpleasant taste usually results in a long-lasting aversion to beads of that type. The present study describes experiments in which pretraining and training were separated by a standard interval and then followed by retention tests at varying times in different groups of Warren sex-link chicks. The effect of variation in the interval between pretraining and training is also examined. Results show that if prior experience ("pretraining") of a bead of the type that is to be used in a later aversive training trial is given to testosterone-treated Ss, it interferes with the retention of avoidance. Interference by pretraining is effective only within sharply defined periods of time: when the pretraining–training interval is either less than 2 min (short-term) or greater than about 25 min (long-term). When pretraining and training are separated by 90 min or more, the steroid can be effective when injected up to 30 min after pretraining. It appears to change the character of the consolidating memory trace of pretraining in such a way as to make the consolidation of later, contradictory information from training less likely. The initial stage of this information is apparantly unaffected, since retention does not begin to decay until 30–60 min after training. Short-term interference leads to loss of avoidance within 5 min of training and can be used to demonstrate that the latency of action of the hormone in this task is less than 20 min following a sc injection. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coproduction of Regan isoenzyme and carcinoembryonic antigen in HCT-8 cells

Five groups of adult Ss were submitted to free-recall learning of 24 objects presented as written nouns for the control group and as pictures for experimental groups, as follows: schematic black and white, schematic colored, detailed black and white, and detailed colored drawings. Pictures were better recalled than nouns. Recall was significantly inferior for schematic black and white than for detailed colored drawings, with schematic colored and detailed black and white drawings at an intermediate level. These results support the so-called incidental-cues hypothesis according to which the best recall of pictures in comparison with that of nouns is partially the result of pictures having more distinctive cues likely to be encoded than do verbal items.     

二重积分计算中的若干技巧

简介了二重积分计算中的若干处理方法，并通过实例加以阐析，对初学者具有一定指导意义。     

Development and validation of the Supervisory Styles Inventory.

Conducted a series of studies to develop and validate the Supervisory Styles Inventory (SSI) with parallel versions for supervisors and trainees. The instrument and validation procedures were based on a conceptual model of interrelated sources of variability among supervisors. Four separate analyses consistently revealed 3 factors among the perceptions of heterogeneous samples of trainees and experienced supervisors, which suggests that supervisory style is multidimensional. Scales constructed from these factors—Attractive, Interpersonally Sensitive, Task Oriented—demonstrated robust reliabilities and construct validity. In one study, SSI scales discriminated within and between expert supervisors with different theoretical orientations working with the same supervisee. These results were consistent with other evidence that a highly task-oriented style is endorsed by cognitive-behavioral supervisors, a highly interpersonal style by psychodynamic and humanistic supervisors. Furthermore, these supervisory styles seem to be differentially related to trainees' level of experience—supervisors are more task oriented with beginners, more attractive and interpersonally sensitive with interns. All 3 styles were strongly associated with trainees' reported willingness to work with different model supervisors and satisfaction with supervision. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bothered by abstraction: The effect of expertise on knowledge transfer and subsequent novice performance.

Although experts should be well positioned to convey their superior knowledge and skill to novices, the organization of that knowledge, and particularly its level of abstraction, may make it difficult for them to do so. Using an electronic circuit-wiring task, the authors found that experts as compared with beginners used more abstract and advanced statements and fewer concrete statements when providing task instructions to novices. In a 2nd study, the authors found that beginner-instructed novices performed better than expert-instructed novices and reported fewer problems with the instructions when performing the same task. In Study 2, the authors found that although novices performed better on the target task when instructed by beginners, they did better on a different task within the same domain when instructed by experts. The evidence suggests that the abstract, advanced concepts conveyed by experts facilitated the transfer of learning between the different tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SEM evaluation of endothelial changes following end-to-side microvascular anastomoses in rats

A scanning electron microscopic (SEM) study was carried out to evaluate the endothelial changes in carotid end-to-side microsurgical anastomoses. This procedure, associated with occlusion of the brachiocephalic trunk, was performed in 24 Sprague-Dawley rats. The animals were sacrificed at time intervals ranging between 15 minutes and 14 days after surgery. The specimens were collected after perfusion-fixation in vivo and treated for SEM observations. The findings show that the first 45 minutes are the most critical time for thrombus formation. Reendothelialization could be detected at 3 days after the microsurgical procedure. Endothelial regeneration occurred earlier on the suture line than on the stitches, documented by the migration and morphological changes of the endothelial cells advancing from the normal endothelium to cover the defect and the suture material. The repair was usually completed within 14 days. Damage of the inner vascular wall, related to minor failures of the microsurgical technique, appears to be a cause of delayed reendothelialization.     

Bead compacts. I. Effect of compression on maintenance of polymer coat integrity in multilayered bead formulations

Little information is available on the compactability of beads for oral sustained-release dosage forms. It is known that polymer-coated beads may fuse together to produce a non-disintegrating controlled-release matrix tablet when compressed. This study evaluates the effect of compression on beads with multiple layers of polymer and drug coat, and the effect of cushioning excipients and compaction pressure on drug release from compressed bead formulations. The multilayered beads consist of several alternating layers of acetaminophen (APAP) and polymer coats (Aquacoat) with an outer layer of mannitol as a cushioning excipient. Percent drug release versus time profiles showed that the release of drug decreases from noncompacted beads as the amount and number of coatings increases, with only 43% of drug released in 24 hr for coated beads with 10 layers. It was shown that the compacted multilayered beads will disintegrate in gastrointestinal fluids, providing a useful drug release pattern. It was shown that beads of drug prepared by any method can be spray-layered with excipients such as Avicel and mannitol. Spray-layering of the cushioning excipient onto beads can provide an effective way to circumvent segregation issues associated with mixing of the polymer-coated beads and powdered or spherical/nonspherical cushioning excipients. Spray layering of the cushioning excipient can also provide excellent flow properties of the final formulation as visually observed in our experiments. Triple-layered caplets (TLC) were also prepared with outer layers of Avicel PH-101 or polyethylene oxide (PEO), and a center layer of polymer-coated beads. For TLC, the polymer coating on the beads fractured, and nondisintegrating matrix formulations were obtained with both caplet formulations.     

Life-span development of visual working memory: When is feature binding difficult?

We asked whether the ability to keep in working memory the binding between a visual object and its spatial location changes with development across the life span more than memory for item information. Paired arrays of colored squares were identical or differed in the color of one square, and in the latter case, the changed color was unique on that trial (item change) or was duplicated elsewhere in the array (color-location binding change). Children (8-10 and 11-12 years old) and older adults (65-85 years old) showed deficits relative to young adults. These were only partly simulated by dividing attention in young adults. The older adults had an additional deficiency, specifically in binding information, which was evident only when item- and binding-change trials were mixed together. In that situation, the older adults often overlooked the more subtle, binding-type changes. Some working memory processes related to binding undergo life-span development in an inverted-U shape, whereas other, bias- and salience-related processes that influence the use of binding information seem to develop monotonically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)