w*a
2 楼
我现在有个summer internship, 于是去学校的 oiss申请CPT。得知要想申请CPT必须
选一门需要工作经验的课? 是这样的吗? 我是数学系的,我们系又没有这样的课,我
就写了一个我导师的independent study。结果oiss认为我之前上independent study不
需要 work experience 所以认为我不需要summer intern,就拒绝了我CPT申请。我该
怎么办呢?
谢谢了!!!!
选一门需要工作经验的课? 是这样的吗? 我是数学系的,我们系又没有这样的课,我
就写了一个我导师的independent study。结果oiss认为我之前上independent study不
需要 work experience 所以认为我不需要summer intern,就拒绝了我CPT申请。我该
怎么办呢?
谢谢了!!!!
f*c
3 楼
这棵自己长出来的苗,在前几天秀出来的时候,曾被某些人认为是应该拔掉而不会挂果
的西红柿,用实际行动向某名ID说:“不是每个地方到了现在都会进入冬眠滴”
女儿曾经有扔金太阳的籽在这里,我以为是金太阳,结果让我有点小失望
再来一张
虽然今天只摘了4颗西红柿,可每颗都长得是那么的标致。
的西红柿,用实际行动向某名ID说:“不是每个地方到了现在都会进入冬眠滴”
女儿曾经有扔金太阳的籽在这里,我以为是金太阳,结果让我有点小失望
再来一张
虽然今天只摘了4颗西红柿,可每颗都长得是那么的标致。
c*7
4 楼
哦也
B*n
5 楼
上次我就说了,不锈钢也不是很安全,尤其是什么国内买,更说不清了,不锈钢分级还
是很严格的,不好的重金属含量严重超标
是很严格的,不好的重金属含量严重超标
S*A
9 楼
有什么方法鉴别这个不锈钢是不是 food grade 的?
我用磁铁试了试,InstantPot 的没有磁性。
大同的电饭锅轻微有磁性。外壳磁性比较多特别是上面一圈
接口出。
我觉得不锈钢本身的毒性应该还好吧。金属只要不溶解于
水,应该问题不大。你想银也是重金属呢,洗胶片的银盐
是千万交代不能倒到下水道的。但是一般人用银器没有什么
忌讳。
水管用铅的,据说只要没有腐蚀问题不太大。我想不锈钢
应该一样,关键是有多少可以进入水里的。其他地方看,
不锈钢还是相对比较安全的。
我用磁铁试了试,InstantPot 的没有磁性。
大同的电饭锅轻微有磁性。外壳磁性比较多特别是上面一圈
接口出。
我觉得不锈钢本身的毒性应该还好吧。金属只要不溶解于
水,应该问题不大。你想银也是重金属呢,洗胶片的银盐
是千万交代不能倒到下水道的。但是一般人用银器没有什么
忌讳。
水管用铅的,据说只要没有腐蚀问题不太大。我想不锈钢
应该一样,关键是有多少可以进入水里的。其他地方看,
不锈钢还是相对比较安全的。
h*k
12 楼
服务员打包带走?
S*A
13 楼
如果没有办法检验,那也是没有办法区别对待。
不粘锅涂层那个明显是高温会分解。比较可怕。
不粘锅涂层那个明显是高温会分解。比较可怕。
T*m
15 楼
就这么几个?还是拔了种秋菜比较好。
r*y
16 楼
还是老祖宗用的铸铁锅放心
y*8
18 楼
好艳丽的国旗红,是小西红柿?
r*y
19 楼
还是老祖宗用的铸铁锅放心
m*6
21 楼
长得是很标致,不过我还是觉得对自己冒出来的杂交二代还是别太认真~~~
l*x
26 楼
我这个学校这个情况也不给办cpt
i*y
29 楼
修改课程大纲啊,因为学校的人对你专业一点都不懂.我去年就是用系里的
independent research course, 自己写课程大纲。不知道你实习的内容跟你专业有多
相关,总之大纲要围绕实习的东西写,这样你去实习就是完成这门课的必须的步骤了。
应该可以通过了吧
independent research course, 自己写课程大纲。不知道你实习的内容跟你专业有多
相关,总之大纲要围绕实习的东西写,这样你去实习就是完成这门课的必须的步骤了。
应该可以通过了吧
m*i
30 楼
哇,红的好正,好标志
s*l
31 楼
那怎么判断啊?家里一堆不锈钢锅。
S*A
33 楼
同问啊,呼叫 BlackQueen。
T*4
38 楼
颜色太正了!
千万别拔了种猪草
千万别拔了种猪草
S*A
43 楼
还是回到如何鉴别得问题啊。
我看了,基本上三档次, 316 最好,但是也没有正式得规范只有
316 可以用在食物处理上。
一般来说 316 》 304 》 430
然后光滑得表面比不光滑得表面好。
关于腐蚀部分,一般还是酸性物质。
所以我想如果自己要测试得话可以用硝酸看看能不能
和不锈钢反应。记得带口罩,硝酸烟吸入有危害。
关键测试还是抗腐蚀性。
抗腐蚀性越高,被认为越安全。至于铬什么得,不锈钢几乎
都有,就是比例不同而已。
Stainless steels used in food processing
Most containers, pipework and food contact equipment in stainless steels is
manufactured from either 304 or 316 type austenitic stainless steels.
The 17% chromium ferritic stainless steel (430 type) is also used widely for
such applications as splashbacks, housings and equipment enclosures, where
corrosion resistance requirements are not so demanding.
In addition to these non-hardenable austenitic and ferritic types higher
strength 'duplex' types, such as grades 1.4362 and 1.4462 are useful for '
warm' conditions (i.e. over 50°C) where stress corrosion cracking (SCC) can
be a corrosion risk, such as in brewery sparge tanks.
Hardenable "martensitic" type stainless steels are widely used for cutting &
grinding applications, especially as knives.
Is 316 type the only stainless steel that is classed as the 'food' grade?
The '316' grades (1.4401 / 1.4404) are often referred to as the 'food'
grades.
There is no known official classification for this and so, depending on the
application, the equally common 1.4301 and 1.4016 grades may be suitable for
food processing and handling, bearing in mind that in general terms the
corrosion resistance ranking of grades can be taken as: -
1.4401/1.4404 (316 types) > 1.4301 (304 types) > 1.4016 (430 types)
Corrosion hazards to stainless steels in food processing
If the grade of stainless steel is correctly specified for the application,
corrosion should not be encountered.
Surface finish and condition is very important to the successful application
of stainless steels. Smooth surfaces not only promote good cleansibility
but also reduce the risk of corrosion.
The types of corrosion to which stainless steels can be susceptible are
summarised below. This can be useful in identifying problems due to wrong
grade selection or inappropriate use of equipment.
Pitting and Crevice Corrosion
Both crevice and pitting corrosion occur most readily in aqueous chloride-
containing solutions. Although attack can occur in neutral conditions,
acidic conditions and increases in temperature promote pitting and crevice
corrosion.
Pitting corrosion is characterised by local deep pits on free surfaces.
Crevice corrosion is occurs in narrow, solution-containing crevices or sharp
re-entrant features in a structure. Examples of potential sites for crevice
corrosion are under washers, flanges and soil deposits or growths on the
stainless steel surface.
Stress Corrosion Cracking
'SCC' is a localised form of corrosion characterised by the appearance of
cracks in materials subject to both stress and a corrosive environment. It
usually occurs in the presence of chlorides at temperatures generally above
50°C.
Intergranular Corrosion
'IGC' or 'ICC' (known in the past as 'weld decay') is the result of
localised attack, generally in a narrow band around heat affected zones of
welds. This is more likely to occur in the 'standard' carbon austenitics.
The risk of IC attack is virtually eliminanted if the low carbon (0.030%
maximum, eg 1.4307) or the 'stabilised' (eg 1.4541) types are selected.
【在 B********n 的大作中提到】![](/moin_static193/solenoid/img/up.png)
: 腐蚀是相对的,你煮个开水,理论上问题不大,但是你不知道自来水中的氯气会不会诱
: 发,做菜就更不好说了,各类调味料一放就……但是相对来说,食品级的应该会好些,
: 但是现在市场上浑水摸鱼,所以就要当心了
我看了,基本上三档次, 316 最好,但是也没有正式得规范只有
316 可以用在食物处理上。
一般来说 316 》 304 》 430
然后光滑得表面比不光滑得表面好。
关于腐蚀部分,一般还是酸性物质。
所以我想如果自己要测试得话可以用硝酸看看能不能
和不锈钢反应。记得带口罩,硝酸烟吸入有危害。
关键测试还是抗腐蚀性。
抗腐蚀性越高,被认为越安全。至于铬什么得,不锈钢几乎
都有,就是比例不同而已。
Stainless steels used in food processing
Most containers, pipework and food contact equipment in stainless steels is
manufactured from either 304 or 316 type austenitic stainless steels.
The 17% chromium ferritic stainless steel (430 type) is also used widely for
such applications as splashbacks, housings and equipment enclosures, where
corrosion resistance requirements are not so demanding.
In addition to these non-hardenable austenitic and ferritic types higher
strength 'duplex' types, such as grades 1.4362 and 1.4462 are useful for '
warm' conditions (i.e. over 50°C) where stress corrosion cracking (SCC) can
be a corrosion risk, such as in brewery sparge tanks.
Hardenable "martensitic" type stainless steels are widely used for cutting &
grinding applications, especially as knives.
Is 316 type the only stainless steel that is classed as the 'food' grade?
The '316' grades (1.4401 / 1.4404) are often referred to as the 'food'
grades.
There is no known official classification for this and so, depending on the
application, the equally common 1.4301 and 1.4016 grades may be suitable for
food processing and handling, bearing in mind that in general terms the
corrosion resistance ranking of grades can be taken as: -
1.4401/1.4404 (316 types) > 1.4301 (304 types) > 1.4016 (430 types)
Corrosion hazards to stainless steels in food processing
If the grade of stainless steel is correctly specified for the application,
corrosion should not be encountered.
Surface finish and condition is very important to the successful application
of stainless steels. Smooth surfaces not only promote good cleansibility
but also reduce the risk of corrosion.
The types of corrosion to which stainless steels can be susceptible are
summarised below. This can be useful in identifying problems due to wrong
grade selection or inappropriate use of equipment.
Pitting and Crevice Corrosion
Both crevice and pitting corrosion occur most readily in aqueous chloride-
containing solutions. Although attack can occur in neutral conditions,
acidic conditions and increases in temperature promote pitting and crevice
corrosion.
Pitting corrosion is characterised by local deep pits on free surfaces.
Crevice corrosion is occurs in narrow, solution-containing crevices or sharp
re-entrant features in a structure. Examples of potential sites for crevice
corrosion are under washers, flanges and soil deposits or growths on the
stainless steel surface.
Stress Corrosion Cracking
'SCC' is a localised form of corrosion characterised by the appearance of
cracks in materials subject to both stress and a corrosive environment. It
usually occurs in the presence of chlorides at temperatures generally above
50°C.
Intergranular Corrosion
'IGC' or 'ICC' (known in the past as 'weld decay') is the result of
localised attack, generally in a narrow band around heat affected zones of
welds. This is more likely to occur in the 'standard' carbon austenitics.
The risk of IC attack is virtually eliminanted if the low carbon (0.030%
maximum, eg 1.4307) or the 'stabilised' (eg 1.4541) types are selected.
【在 B********n 的大作中提到】
![](/moin_static193/solenoid/img/up.png)
: 腐蚀是相对的,你煮个开水,理论上问题不大,但是你不知道自来水中的氯气会不会诱
: 发,做菜就更不好说了,各类调味料一放就……但是相对来说,食品级的应该会好些,
: 但是现在市场上浑水摸鱼,所以就要当心了
S*A
45 楼
查了, FDA 没有规定什么样的不锈钢可以用于食物处理。
有人专门去问了,这个回信是最接近回答这个问题的:
They just send me a general e-mail ....
Thank you for writing the Division of Drug Information, in the FDA's Center
for Drug Evaluation and Research (CDER).
FDA does not approve or prohibit specific materials used in contact with
pharmaceutical products or maintain a schedule or list of approved materials
. 21 CFR 211.65 requires equipment (surfaces that contact) components, in-
process materials, or drug products shall not be reactive, additive, or
absorptive so as to alter the safety, identity, strength, quality, or purity
of the drug product beyond the official or other established requirements.
21 CFR 211.63 requires that equipment (surfaces that contact) be of
appropriate design to facilitate operations for its intended use and for
cleaning and maintenance. 21 CFR 211.67 requires firms to clean, maintain,
and sanitize equipment (surfaces that contact) at appropriate intervals to
prevent malfunctions or contamination that would adversely affect product
quality.
Here is a link to 21 CFR 211, http://www.access.gpo.gov/nara/cfr/w...cfr211_04.html.
Firms are afforded the flexibility to select the materials and grade that
best satisfies the needs of their particular application. CGMP regulations
do not include specifics on stainless steel.
In choosing materials or components involves evaluating whether there is any
potential for an adverse impact on drug product quality. In this respect,
various compatibility considerations (leachables, interaction with
formulations/sanitizers, ability of material to withstand sterilization) can
often take on the most CGMP significance.
Which isn't really useful
有人专门去问了,这个回信是最接近回答这个问题的:
They just send me a general e-mail ....
Thank you for writing the Division of Drug Information, in the FDA's Center
for Drug Evaluation and Research (CDER).
FDA does not approve or prohibit specific materials used in contact with
pharmaceutical products or maintain a schedule or list of approved materials
. 21 CFR 211.65 requires equipment (surfaces that contact) components, in-
process materials, or drug products shall not be reactive, additive, or
absorptive so as to alter the safety, identity, strength, quality, or purity
of the drug product beyond the official or other established requirements.
21 CFR 211.63 requires that equipment (surfaces that contact) be of
appropriate design to facilitate operations for its intended use and for
cleaning and maintenance. 21 CFR 211.67 requires firms to clean, maintain,
and sanitize equipment (surfaces that contact) at appropriate intervals to
prevent malfunctions or contamination that would adversely affect product
quality.
Here is a link to 21 CFR 211, http://www.access.gpo.gov/nara/cfr/w...cfr211_04.html.
Firms are afforded the flexibility to select the materials and grade that
best satisfies the needs of their particular application. CGMP regulations
do not include specifics on stainless steel.
In choosing materials or components involves evaluating whether there is any
potential for an adverse impact on drug product quality. In this respect,
various compatibility considerations (leachables, interaction with
formulations/sanitizers, ability of material to withstand sterilization) can
often take on the most CGMP significance.
Which isn't really useful
M*7
46 楼
几天前看还是花,现在西红柿都这么红了.南加真是好地方.
B*n
47 楼
恩,越是模糊越是要当心
所以我现在也不那么排斥不粘了。。。⊙﹏⊙b汗
风口浪尖的东西,至少测试过在哪些情况下是安全的了
Center
materials
purity
【在 S*A 的大作中提到】![](/moin_static193/solenoid/img/up.png)
: 查了, FDA 没有规定什么样的不锈钢可以用于食物处理。
: 有人专门去问了,这个回信是最接近回答这个问题的:
: They just send me a general e-mail ....
: Thank you for writing the Division of Drug Information, in the FDA's Center
: for Drug Evaluation and Research (CDER).
: FDA does not approve or prohibit specific materials used in contact with
: pharmaceutical products or maintain a schedule or list of approved materials
: . 21 CFR 211.65 requires equipment (surfaces that contact) components, in-
: process materials, or drug products shall not be reactive, additive, or
: absorptive so as to alter the safety, identity, strength, quality, or purity
所以我现在也不那么排斥不粘了。。。⊙﹏⊙b汗
风口浪尖的东西,至少测试过在哪些情况下是安全的了
Center
materials
purity
【在 S*A 的大作中提到】
![](/moin_static193/solenoid/img/up.png)
: 查了, FDA 没有规定什么样的不锈钢可以用于食物处理。
: 有人专门去问了,这个回信是最接近回答这个问题的:
: They just send me a general e-mail ....
: Thank you for writing the Division of Drug Information, in the FDA's Center
: for Drug Evaluation and Research (CDER).
: FDA does not approve or prohibit specific materials used in contact with
: pharmaceutical products or maintain a schedule or list of approved materials
: . 21 CFR 211.65 requires equipment (surfaces that contact) components, in-
: process materials, or drug products shall not be reactive, additive, or
: absorptive so as to alter the safety, identity, strength, quality, or purity
S*A
49 楼
这个查的是 CDER,制药业, 因为 CDER 有对不锈钢进行等级分类。
食物好像还没有那么严格。
食物好像还没有那么严格。
M*s
53 楼
看到楼上的言论,我也认为不锈钢靠谱点,至少没涂层可脱落。
C*2
54 楼
漂亮啊!
z*e
70 楼
又红又圆很漂亮啊!
应该也是酸甜可口!
应该也是酸甜可口!
o*p
76 楼
表闹表闹,菜都没做好呢连怎么用不锈钢锅不沾都不知道呢就开始担心吃出病来,太超
前了吧?人鬼子用几十年的不锈钢锅都没事好吧。
前了吧?人鬼子用几十年的不锈钢锅都没事好吧。
e*s
77 楼
可怕。
t*g
82 楼
固态剧毒应该是食用人口14天内的 LD50<=50mg/kg
可行的方法是用不锈钢内胆高压锅, 比如说instant pot
煮醋24小时, 然后用醋灌喂小鼠, 这样7 7 49天以后, 和对比组
对比重金属的toxicology report, 使用前的对比也是需要的
碱性物质也是需要的, 但是没有酸性物质那么重要
可行的方法是用不锈钢内胆高压锅, 比如说instant pot
煮醋24小时, 然后用醋灌喂小鼠, 这样7 7 49天以后, 和对比组
对比重金属的toxicology report, 使用前的对比也是需要的
碱性物质也是需要的, 但是没有酸性物质那么重要
S*A
89 楼
多谢多谢 datasheet。
这个没有直接比较比较 316L 和 304L。
304L 之所以要分类列出来有一大堆可以抵抗的, 主要是有一些
是不可以抵抗的,你贴出来的就有,特别是硫化物就不行。
所以这个要分别交代。
316L 那个 datasheet 一开始就说,”special design application
requiring resistance to senitiation and intergranular corrosion."
这个抗腐蚀的设计在 304L 里面没有。
然后后面还有说, 316L 可以用在 800F-1600F 这种通常不锈钢
是不适合用的场合。316L 没有分类列出那些可以抵抗,那些不可以
抵抗。我觉得这个这个在 316L是为抗腐蚀这个设计目的下,可以
暗示是没有 304 的缺点。
而且你仔细看看 316L 的腐蚀性那章,专门讨论了氧化不均匀和不
锈钢表面有沉淀物。大家的不锈钢锅是不是旧的就没有新的靓丽?
有些暗点不容易去掉?这章最后这句特别給力,我抄一下:
316L is recommend for application for this type(上文讨论了
接触氧化的腐蚀)due to its superior resistance to contract
corrosion.
就是说,抗腐蚀这章,没有讲 316L 的弱点,什么地方不能用,只
是强调了 316L 的优点,说抗腐蚀是 316L 长处,建议使用。
结论 316L 抗腐蚀性强于 304L 很明显啊。
【在 t******g 的大作中提到】![](/moin_static193/solenoid/img/up.png)
: 真的很可怜。。。
: 喂没有浸泡过的醋的组, 可以有
: 300 号不锈钢是 crucible 出的
: 具体成分都能查到
: 304的抗腐蚀性在datasheet 里面说地要比316 要多
这个没有直接比较比较 316L 和 304L。
304L 之所以要分类列出来有一大堆可以抵抗的, 主要是有一些
是不可以抵抗的,你贴出来的就有,特别是硫化物就不行。
所以这个要分别交代。
316L 那个 datasheet 一开始就说,”special design application
requiring resistance to senitiation and intergranular corrosion."
这个抗腐蚀的设计在 304L 里面没有。
然后后面还有说, 316L 可以用在 800F-1600F 这种通常不锈钢
是不适合用的场合。316L 没有分类列出那些可以抵抗,那些不可以
抵抗。我觉得这个这个在 316L是为抗腐蚀这个设计目的下,可以
暗示是没有 304 的缺点。
而且你仔细看看 316L 的腐蚀性那章,专门讨论了氧化不均匀和不
锈钢表面有沉淀物。大家的不锈钢锅是不是旧的就没有新的靓丽?
有些暗点不容易去掉?这章最后这句特别給力,我抄一下:
316L is recommend for application for this type(上文讨论了
接触氧化的腐蚀)due to its superior resistance to contract
corrosion.
就是说,抗腐蚀这章,没有讲 316L 的弱点,什么地方不能用,只
是强调了 316L 的优点,说抗腐蚀是 316L 长处,建议使用。
结论 316L 抗腐蚀性强于 304L 很明显啊。
【在 t******g 的大作中提到】
![](/moin_static193/solenoid/img/up.png)
: 真的很可怜。。。
: 喂没有浸泡过的醋的组, 可以有
: 300 号不锈钢是 crucible 出的
: 具体成分都能查到
: 304的抗腐蚀性在datasheet 里面说地要比316 要多
t*g
90 楼
嗯, 应该是这样的,
其实crucible 有corrosion resistance datasheet
不过我没找到。
其实我觉得除了钢材, 制造过程对钢以后的抗腐蚀性也挺重要的
也就是说, 从毛胚到电锅的内胆的锻造过程如果一个重要指标不达标
比如说温度
这就是为啥datasheet对 锻造退火和淬火都有温度指示
【在 S*A 的大作中提到】![](/moin_static193/solenoid/img/up.png)
: 多谢多谢 datasheet。
: 这个没有直接比较比较 316L 和 304L。
: 304L 之所以要分类列出来有一大堆可以抵抗的, 主要是有一些
: 是不可以抵抗的,你贴出来的就有,特别是硫化物就不行。
: 所以这个要分别交代。
: 316L 那个 datasheet 一开始就说,”special design application
: requiring resistance to senitiation and intergranular corrosion."
: 这个抗腐蚀的设计在 304L 里面没有。
: 然后后面还有说, 316L 可以用在 800F-1600F 这种通常不锈钢
: 是不适合用的场合。316L 没有分类列出那些可以抵抗,那些不可以
其实crucible 有corrosion resistance datasheet
不过我没找到。
其实我觉得除了钢材, 制造过程对钢以后的抗腐蚀性也挺重要的
也就是说, 从毛胚到电锅的内胆的锻造过程如果一个重要指标不达标
比如说温度
这就是为啥datasheet对 锻造退火和淬火都有温度指示
【在 S*A 的大作中提到】
![](/moin_static193/solenoid/img/up.png)
: 多谢多谢 datasheet。
: 这个没有直接比较比较 316L 和 304L。
: 304L 之所以要分类列出来有一大堆可以抵抗的, 主要是有一些
: 是不可以抵抗的,你贴出来的就有,特别是硫化物就不行。
: 所以这个要分别交代。
: 316L 那个 datasheet 一开始就说,”special design application
: requiring resistance to senitiation and intergranular corrosion."
: 这个抗腐蚀的设计在 304L 里面没有。
: 然后后面还有说, 316L 可以用在 800F-1600F 这种通常不锈钢
: 是不适合用的场合。316L 没有分类列出那些可以抵抗,那些不可以
l*e
91 楼
看这么多都晕。谁能说说INSTANT POT的电压力锅有没有问题?
S*A
93 楼
其实应该有更加便宜的方法。可以买些标准的 316L, 304L 和一个 Instant Pot。
一起滴硝酸上去,看看反应如何,有没有黄色的斑。然后滴热的硝酸,看看。
我比较喜爱我自己的 Instant Pot, 不舍得拿出来滴硝酸。
一起滴硝酸上去,看看反应如何,有没有黄色的斑。然后滴热的硝酸,看看。
我比较喜爱我自己的 Instant Pot, 不舍得拿出来滴硝酸。
c*s
94 楼
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