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简述耐热合金中元素碳,钒各起什么作用?

答案

参考答案:

碳的作用:耐热钢中一般都含有一定量的碳元素,碳对钢的强度影响很大,但在高温和长期运行的条件下,碳元素又是造成组织不稳定的主要因素,而且随着含碳量增加,钢的组织不稳定性也增大,也使钢的可焊性和冷变形等工艺性能变坏。钒的作用:钒是强碳化物形成的元素,在钢中能够形成细小均匀,高度分散的碳化物和氮化物微粒,可以阻碍碳化物的聚集长大以及减小铬,钼等元素在固溶体里贫化的趋势,从而使钢的组织稳定性和抗蠕变能力提高,耐热钢的钒含量,一般均小于0.4%,这是因为,含钒量更大时,所形成的碳化物将要粗化,对钢的热强性反而有害。

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Social-networking sites offer users easy ways to present idealized images of themselves, even if those ideals don’t always square with their real-world personalities. Psychology researcher Soraya Mehdizadeh has discovered a way to poke through the offline-online curtain: she has used Faeebook to predict a person’s level of narcissism and self-esteem.

Mehdizadeh, who conducted the study as an undergraduate at Toronto’s York University, gained access to the Faeebook accounts of 100 college students and measured activities like photo sharing, wall postings and status updates; she also studied how frequently users logged on and how often they remained online during each session. Her findings were published recently in Cyberpsyehology, Behavior and Social Networking.

After measuring each subject using the Narcissism Personality Inventory and Rosenberg Self-Esteem Scale, Mehdizadeh, who graduated from York this past spring, discovered narcissists and people with lower self-esteem were more likely to spend more than an hour a day on Facebook and were more prone to post self-promo-tional photos ( striking a pose or using Photoshop, for example). Narcissists were also more likely to showcase themselves through status updates (using phrases like "I’m so glamorous I bleed glitter") and wall activity (posting self-serving links like " My Celebrity Look-alikes" ).

Self-esteem and narcissism are often interrelated but don’t always go hand in hand. Some psychologists believe that narcissists--those who have a pervasive pattern of grandiosity, a need for admiration, as well as a lack of sympathy--unconsciously inflate their sense of self-importance as a defense against feeling inadequate. Not enough empirical research has been produced to confirm that link, although Mehdizadeh’s study seems to support it. Because narcissists have less capacity to sustain intimate or long-term relationships, Mehdizadeh thinks that they would be more drawn to the online world of virtual friends and emotionally detached communication.

Although it seems that Facebook can be used by narcissists to fuel their inflated egos, Mehdizadeh stops short of proclaiming that excessive time spent on Faeebook can turn regular users into narcissists. She also notes that social-networking sites might ultimately be found to have positive effects when used by people with low self-esteem or depression. "If individuals with lower self-esteem are more prone to using Facebook," she says, "the question becomes, ’ Can Facebook help raise self- esteem by allowing patients to talk to each other and help each other in a socially interactive environment’ I don’t think it’s necessarily a bad thing that people with low self-esteem use Facebook.

Mehdizadeh may think that()

A.Facebook will make people abnormal

B. people with low self-esteem could increase their confidence by Facebook

C. Facebook is socially interactive environment

D. narcissists with lower self-esteem don’t like to communicate mood