Large-area Silicon-FilmTM manufacturing
Title:Large-area Silicon-FilmTM manufacturing
Authors:; ; ; ; ; ; ; ;
Affiliation:AA(AstroPower, Inc., Solar Park, Newark, Delaware ), AB(AstroPower, Inc., Solar Park, Newark, Delaware ), AC(AstroPower, Inc., Solar Park, Newark, Delaware ), AD(AstroPower, Inc., Solar Park, Newark, Delaware ), AE(AstroPower, Inc., Solar Park, Newark, Delaware ), AF(AstroPower, Inc., Solar Park, Newark, Delaware ), AG(AstroPower, Inc., Solar Park, Newark, Delaware ), AH(AstroPower, Inc., Solar Park, Newark, Delaware ), AI(AstroPower, Inc., Solar Park, Newark, Delaware )
Publication:The 13th NREL photovoltaics program review meeting. AIP Conference Proceedings, Volume 353, pp. 283-289 (1996). ()
Publication Date:01/1996
PACS Keywords:Photoconduction and photovoltaic effects, Photoelectric conversion: solar cells and arrays, Performance characteristics of energy conversion systems, figure of merit
Abstract Copyright:1996: American Institute of Physics
Bibliographic Code:
In three years, AstroPower's Silicon-FilmTM
program has grown from a laboratory batch process making 100
cm2 solar cells to a continuous manufacturing process used to
fabricate a 20 kW array of modules made with 240 cm2 cells.
Under the PVMaT-2A program AstroPower has established a
Silicon-FilmTM sheet production capacity of 4.5
MW/year. Significant advances were made in sheet production, device
fabrication, and device and module efficiency. In developing a low-cost
process, the focus has been on limiting the consumption of high quality
silicon, reducing sawing requirements, and utilizing a high yield
continuous manufacturing technology. Key device results include the
verification of a 2.9 watt solar cell using the 240 cm2
substrate (12.2%) and 7.9 watt solar cell on a 676 cm2
substrate (11.7%). AstroPower's manufacturing plans include a sheet
production capability of 20 MW/year over the next three years. Initial
production runs were used to successfully fabricate and install a
nominal 20 kW array for the PVUSA program.
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＞＞＞标准状况下VL氨气溶解在1L水中（水的密度近似为1g/mL），所得溶液的..
标准状况下VL氨气溶解在1L水中（水的密度近似为1g/mL），所得溶液的密度为ρg/mL，质量分数为W，物质的量浓度为cmol/L，则下列关系中不正确的是（　　）A．W=17c1000ρB．W=17V17V+22400C．ρ=17V+2240022.4+22.4VD．c=1000Vρ17V+22400
题型：单选题难度：偏易来源：不详
A、根据c=1000ρwM可知，该氨水质量分数w=17c1000ρ，故A正确；B、VL氨气的物质的量为VL22.4L/mol=V22.4mol，氨气质量为V22.4mol×17g．mol=17V22.4g，1L水的质量为1000mL×1g/mL=1000g，故溶液质量为（17V22.4+1000）g，所以溶液的质量分数w=17V22.4g(17V22.4+1000)g×100%=17V17V+22400×100%，故B正确；C、VL氨气的物质的量为VL22.4L/mol=V22.4mol，氨气质量为V22.4mol×17g．mol=17V22.4g，1L水的质量为1000mL×1g/mL=1000g，故溶液质量为（17V22.4+1000）g，溶液体积为V22.4molcmol/L=V22.4cL，所以溶液的密度为(17V22.4+1000)gV22.4c×103mL=17cV+22400c1000V，故C错误；D、VL氨气的物质的量为VL22.4L/mol=V22.4mol，氨气质量为V22.4mol×17g．mol=17V22.4g，1L水的质量为1000mL×1g/mL=1000g，故溶液质量为（17V22.4+1000）g，溶液体积为(17V22.4+1000)g1000ρg/L=17V+2240022400ρL，所以物质的量浓度c=V22.4mol17V+2240022400ρL=1000Vρ17V+22400mol/L，故D正确；故选C．
马上分享给同学
据魔方格专家权威分析，试题“标准状况下VL氨气溶解在1L水中（水的密度近似为1g/mL），所得溶液的..”主要考查你对&&物质的量浓度&&等考点的理解。关于这些考点的“档案”如下：
现在没空？点击收藏，以后再看。
因为篇幅有限，只列出部分考点，详细请访问。
物质的量浓度
物质的量浓度：
定义：单位体积的溶液里所含溶质B的物质的量，也称为B的物质的量浓度 符号：cB 单位：mol/L(mol·L -1)计算公式：物质的量浓度(cB)=物质的量(n)/溶液的体积(V) 物质的量浓度与溶液质量分数、密度的关系：c=1000ρω/M 稀释定理：
稀释前后溶液中溶质的物质的量不变c(浓溶液)V(浓溶液)=c(稀溶液)V(稀溶液)
稀释前后溶液中溶质的质量不变ρ(浓溶液)V(浓溶液)w%(浓溶液)=ρ(稀溶液)V(稀溶液)w%(稀溶液)物质的量浓度与质量分数(质量百分比浓度)的比较:
&&浓度计算的注意事项：
物质的量浓度(cB)=物质的量(n)/溶液的体积(V)（1）V指溶液体积而不是溶剂的体积；（2）取出任意体积的1mol/L溶液，其浓度都是1mol/L。但所含溶质的量则因体积不同而不同；（3）“溶质”是溶液中的溶质，可以是化合物，也可以是离子或气体特定组合，特别的，像NH3、Cl2等物质溶于水后成分复杂，但求算浓度时，仍以溶解前的NH3、Cl2为溶质，如氨水在计算中使用摩尔质量时，用17g/mol。&溶液中溶质的质量分数与溶质的物质的量浓度的换算:
溶液中溶质的质量可以用溶质的质量分数表示:& m(溶质)=ρ(g·cm-3)·V(L)·w%&&& &(1cm3=1mL)
溶液中溶质的质量可以用物质的量浓度来表示:&&m(溶质)=c(mol/L)·V(L)·M(g·mol-1)
由于同一溶液中溶质的质量相等，溶液的体积也相等，但注意：1L=1000mL,所以，上述两式可以联系起来：ρ(g·cm-3)·1000V(mL)·w%=c(mol/L)·V(L)·M(g·mol-1) 化简得：1000ρw%=cM
发现相似题
与“标准状况下VL氨气溶解在1L水中（水的密度近似为1g/mL），所得溶液的..”考查相似的试题有：
2027511002727496820416920205199884From Wikipedia, the free encyclopedia
This article has multiple issues. Please help
or discuss these issues on the . ()
Prior to public key methods like Diffie–Hellman, cryptographic keys had to be transmitted in physical form such as this World War II list of keys for the German .
Diffie–Hellman key exchange (DH) is a method of securely exchanging
over a public channel and was one of the first
as originally conceptualized by
and named after
and . DH is one of the earliest practical examples of public
implemented within the field of .
Traditionally, secure encrypted communication between two parties required that they first exchange keys by some secure physical channel, such as paper key lists transported by a trusted . The Diffie–Hellman key exchange method allows two parties that have no prior knowledge of each other to jointly establish a
key over an
. This key can then be used to encrypt subsequent communications using a
Diffie–Hellman is used to secure a variety of
services. However, research published in October 2015 suggests that the parameters in use for many DH Internet applications at that time are not strong enough to prevent compromise by very well-funded attackers, such as the security services of large governments.
The scheme was first published by Whitfield Diffie and Martin Hellman in 1976, but in 1997 it was revealed that ,
of , the British signals intelligence agency, had previously, in 1969, shown how public-key cryptography could be achieved.
Although Diffie–Hellman key agreement itself is a non-authenticated , it provides the basis for a variety of authenticated protocols, and is used to provide
modes (referred to as EDH or DHE depending on the cipher suite).
The method was followed shortly afterwards by , an implementation of
using asymmetric algorithms.
from 1977, is now expired and describes the now-public domain algorithm. It credits Hellman, Diffie, and Merkle as inventors.
In 2002, Hellman suggested the algorithm be called Diffie–Hellman–Merkle key exchange in recognition of 's contribution to the invention of
(Hellman, 2002), writing:
The system...has since become known as Diffie–Hellman key exchange. While that system was first described in a paper by Diffie and me, it is a public key distribution system, a concept developed by Merkle, and hence should be called 'Diffie–Hellman–Merkle key exchange' if names are to be associated with it. I hope this small pulpit might help in that endeavor to recognize Merkle's equal contribution to the invention of public key cryptography.
Illustration of the idea behind Diffie–Hellman key Exchange
Diffie–Hellman Key Exchange establishes a shared secret between two parties that can be used for secret communication for exchanging data over a public network. The following conceptual diagram illustrates the general idea of the key exchange by using colors instead of very large numbers.
The process begins by having the two parties, , agree on an arbitrary starting color that does not need to be kept secret (but should be different every time); in this example the color is yellow. Each of them selects a secret color that they keep to themselves. In this case, orange and blue-green. The crucial part of the process is that Alice and Bob now mix their secret color together with their mutually shared color, resulting in orange-tan and light-blue mixtures respectively, then publicly exchange the two mixed colors. Finally, each of the two mix together the color they received from the partner with their own private color. The result is a final color mixture yellow-brown that is identical to the partner's color mixture.
If a third party listened to the exchange, it would be computationally difficult for them to determine the secret colors. In fact, when using large numbers rather than colors, this action is computationally expensive for modern
to do in a reasonable amount of time.
The simplest and the original implementation of the protocol uses the
p, where p is , and g is a
p. These two values are chosen in this way to ensure that the resulting shared secret can take on any value from 1 to p–1. Here is an example of the protocol, with non-secret values in blue, and secret values in red.
agree to use a modulus p = 23 and base g = 5 (which is a
Alice chooses a secret integer a = 4, then sends Bob A = ga mod p
A = 54 mod 23 = 4
Bob chooses a secret integer b = 3, then sends Alice B = gb mod p
B = 53 mod 23 = 10
Alice computes s = Ba mod p
s = 104 mod 23 = 18
Bob computes s = Ab mod p
s = 43 mod 23 = 18
Alice and Bob now share a secret (the number 18).
Both Alice and Bob have arrived at the same value s, because, under mod p,
{\displaystyle {\color {Blue}A}^{\color {Red}b}{\bmod {\color {Blue}p}}={\color {Blue}g}^{\color {Red}ab}{\bmod {\color {Blue}p}}={\color {Blue}g}^{\color {Red}ba}{\bmod {\color {Blue}p}}={\color {Blue}B}^{\color {Red}a}{\bmod {\color {Blue}p}}}
More specifically,
{\displaystyle ({\color {Blue}g}^{\color {Red}a}{\bmod {\color {Blue}p}})^{\color {Red}b}{\bmod {\color {Blue}p}}=({\color {Blue}g}^{\color {Red}b}{\bmod {\color {Blue}p}})^{\color {Red}a}{\bmod {\color {Blue}p}}}
Note that only a, b, and (gab mod p = gba mod p) are kept secret. All the other values – p, g, ga mod p, and gb mod p – are sent in the clear. Once Alice and Bob compute the shared secret they can use it as an encryption key, known only to them, for sending messages across the same open communications channel.
Of course, much larger values of a, b, and p would be needed to make this example secure, since there are only 23 possible results of n mod 23. However, if p is a prime of at least 600 digits, then even the fastest modern computers cannot find a given only g, p and ga mod p. Such a problem is called the . The computation of ga mod p is known as
and can be done efficiently even for large numbers. Note that g need not be large at all, and in practice is usually a small integer (like 2, 3, ...).
The chart below depicts who knows what, again with non-secret values in blue, and secret values in red. Here
is an —she watches what is sent between Alice and Bob, but she does not alter the contents of their communications.
g = public (prime) base, known to Alice, Bob, and Eve. g = 5
p = public (prime) modulus, known to Alice, Bob, and Eve. p = 23
a = Alice's private key, known only to Alice. a = 6
b = Bob's private key known only to Bob. b = 15
A = Alice's public key, known to Alice, Bob, and Eve. A = ga mod p = 8
B = Bob's public key, known to Alice, Bob, and Eve. B = gb mod p = 19
A = 5a mod 23
A = 56 mod 23 = 8
s = Ba mod 23
s = 196 mod 23 = 2
B = 5b mod 23
B = 515 mod 23 = 19
s = Ab mod 23
s = 815 mod 23 = 2
A = 8, B = 19
Now s is the shared secret key and it is known to both Alice and Bob, but not to Eve.
Note: It should be difficult for Alice to solve for Bob's private key or for Bob to solve for Alice's private key. If it is not difficult for Alice to solve for Bob's private key (or vice versa), Eve may simply substitute her own private / public key pair, plug Bob's public key into her private key, produce a fake shared secret key, and solve for Bob's private key (and use that to solve for the shared secret key. Eve may attempt to choose a public / private key pair that will make it easy for her to solve for Bob's private key).
Another demonstration of Diffie–Hellman (also using numbers too small for practical use) is given .
Here is a more general description of the protocol:
Alice and Bob agree on a finite
G of order n and a
element g in G. (This is usually done long before the
g is assumed to be known by all attackers.) The group G is written multiplicatively.
Alice picks a random
a, where 1 ≤ a & n, and sends ga to Bob.
Bob picks a random natural number b, which is also 1 ≤ b & n, and sends gb to Alice.
Alice computes (gb)a.
Bob computes (ga)b.
Both Alice and Bob are now in possession of the group element gab, which can serve as the shared secret key. The group G satisfies the requisite condition for secure communication if there is not an efficient algorithm for determining gab given g, ga, and gb.
For example, the
protocol is variant that uses elliptic curves instead of the multiplicative group of integers modulo p. Variants using
have also been proposed. The
is a Diffie–Hellman variant that has been designed to be secure against quantum computers.
Diffie–Hellman key agreement is not limited to negotiating a key shared by only two participants. Any number of users can take part in an agreement by performing iterations of the agreement protocol and exchanging intermediate data (which does not itself need to be kept secret). For example, Alice, Bob, and Carol could participate in a Diffie–Hellman agreement as follows, with all operations taken to be modulo p:
The parties agree on the algorithm parameters p and g.
The parties generate their private keys, named a, b, and c.
Alice computes ga and sends it to Bob.
Bob computes (ga)b = gab and sends it to Carol.
Carol computes (gab)c = gabc and uses it as her secret.
Bob computes gb and sends it to Carol.
Carol computes (gb)c = gbc and sends it to Alice.
Alice computes (gbc)a = gbca = gabc and uses it as her secret.
Carol computes gc and sends it to Alice.
Alice computes (gc)a = gca and sends it to Bob.
Bob computes (gca)b = gcab = gabc and uses it as his secret.
An eavesdropper has been able to see ga, gb, gc, gab, gac, and gbc, but cannot use any combination of these to efficiently reproduce gabc.
To extend this mechanism to larger groups, two basic principles must be followed:
Starting with an "empty" key consisting only of g, the secret is made by raising the current value to every participant’s private exponent once, in any order (the first such exponentiation yields the participant’s own public key).
Any intermediate value (having up to N-1 exponents applied, where N is the number of participants in the group) may be revealed publicly, but the final value (having had all N exponents applied) constitutes the shared secret and hence must never be revealed publicly. Thus, each user must obtain their copy of the secret by applying their own private key last (otherwise there would be no way for the last contributor to communicate the final key to its recipient, as that last contributor would have turned the key into the very secret the group wished to protect).
These principles leave open various options for choosing in which order participants contribute to keys. The simplest and most obvious solution is to arrange the N participants in a circle and have N keys rotate around the circle, until eventually every key has been contributed to by all N participants (ending with its owner) and each participant has contributed to N keys (ending with their own). However, this requires that every participant perform N modular exponentiations.
By choosing a more optimal order, and relying on the fact that keys can be duplicated, it is possible to reduce the number of modular exponentiations performed by each participant to log2(N) + 1 using a
approach, given here for eight participants:
Participants A, B, C, and D each perform one exponentiation, yielding gabcd; this value is sent to E, F, G, and H. In return, participants A, B, C, and D receive gefgh.
Participants A and B each perform one exponentiation, yielding gefghab, which they send to C and D, while C and D do the same, yielding gefghcd, which they send to A and B.
Participant A performs an exponentiation, yielding gefghcda, which it sends to B; similarly, B sends gefghcdb to A. C and D do similarly.
Participant A performs one final exponentiation, yielding the secret gefghcdba = gabcdefgh, while B does the same to get gefghcdab = gabcdefgh; again, C and D do similarly.
Participants E through H simultaneously perform the same operations using gabcd as their starting point.
Once this operation has been completed all participants will possess the secret gabcdefgh, but each participant will have performed only four modular exponentiations, rather than the eight implied by a simple circular arrangement.
The protocol is considered secure against eavesdroppers if G and g are chosen properly. In particular, the order of the group G must be large, particularly if the same group is used for large amounts of traffic. The eavesdropper ("") has to solve the
to obtain gab. This is currently considered difficult for groups whose order is large enough. An efficient algorithm to solve the
would make it easy to compute a or b and solve the Diffie–Hellman problem, making this and many other public key cryptosystems insecure. Fields of small characteristic may be less secure.
of G should have a large prime factor to prevent use of the
to obtain a or b. For this reason, a
q is sometimes used to calculate p = 2q + 1, called a , since the order of G is then only divisible by 2 and q. g is then sometimes chosen to generate the order q subgroup of G, rather than G, so that the
of ga never reveals the low order bit of a. A protocol using such a choice is for example .
g is often a small integer such as 2. Because of the
of the discrete logarithm problem a small g is equally secure as any other generator of the same group.
If Alice and Bob use
whose outputs are not completely random and can be predicted to some extent, then Eve's task is much easier.
In the original description, the Diffie–Hellman exchange by itself does not provide
of the communicating parties and is thus vulnerable to a .
(an active attacker executing the man-in-the-middle attack) may establish two distinct key exchanges, one with Alice and the other with Bob, effectively masquerading as Alice to Bob, and vice versa, allowing her to decrypt, then re-encrypt, the messages passed between them. Note that Mallory must continue to be in the middle, transferring messages every time Alice and Bob communicate. If she is ever absent, her previous presence is then revealed to Alice and Bob. They will know that all of their private conversations had been intercepted and decoded by someone in the channel.
A method to authenticate the communicating parties to each other is generally needed to prevent this type of attack. Variants of Diffie–Hellman, such as , may be used instead to avoid these types of attacks.
algorithm, which is generally the most effective in solving the , consists of four computational steps. The first three steps only depend on the order of the group G, not on the specific number whose finite log is desired. It turns out that much Internet traffic uses one of a handful of groups that are of order ;bits or less. By
the first three steps of the number field sieve for the most common groups, an attacker need only carry out the last step, which is much less computationally expensive than the first three steps, to obtain a specific logarithm. The
attack used this vulnerability to compromise a variety of Internet services that allowed the use of groups whose order was a 512-bit prime number, so called . The authors needed several thousand CPU cores for a week to precompute data for a single 512-bit prime. Once that was done, individual logarithms could be solved in about a minute using two 18-core Intel Xeon CPUs.
As estimated by the authors behind the Logjam attack, the much more difficult precomputation needed to solve the discrete log problem for a 1024-bit prime would cost on the order of $100 million, well within the budget of large national
such as the U.S.
(NSA). The Logjam authors speculate that precomputation against widely reused 1024-bit DH primes is behind claims in
that NSA is able to break much of current cryptography.
To avoid these vulnerabilities, authors recommend use of , for which no similar attack is known. Failing that, they recommend that the order, p, of the Diffie–Hellman group should be at least ;bits. They estimate that the pre-computation required for a 2048-bit prime is 109 more difficult than for 1024-bit primes.
If NSA is breaking Diffie–Hellman, but has not pushed for US sites to upgrade to longer keys, then it would be an example of NSA's
policy of not closing security holes that NSA believes only they can exploit.
Public key encryption schemes based on the Diffie–Hellman key exchange have been proposed. The first such scheme is the . A more modern variant is the .
Protocols that achieve
generate new key pairs for each
and discard them at the end of the session. The Diffie–Hellman key exchange is a frequent choice for such protocols, because of its fast key generation.
When Alice and Bob share a password, they may use a
(PK) form of Diffie–Hellman to prevent man-in-the-middle attacks. One simple scheme is to compare the
of s concatenated with the password calculated independently on both ends of channel. A feature of these schemes is that an attacker can only test one specific password on each iteration with the other party, and so the system provides good security with relatively weak passwords. This approach is described in
Recommendation , which is used by the
home networking standard.
An example of such a protocol is the .
It is also possible to use Diffie–Hellman as part of a , allowing Bob to encrypt a message so that only Alice will be able to decrypt it, with no prior communication between them other than Bob having trusted knowledge of Alice's public key. Alice's public key is
{\displaystyle (g^{a}{\bmod {p}},g,p)}
. To send her a message, Bob chooses a random b and then sends Alice
{\displaystyle g^{b}{\bmod {p}}}
(un-encrypted) together with the message encrypted with symmetric key
{\displaystyle (g^{a})^{b}{\bmod {p}}}
. Only Alice can determine the symmetric key and hence decrypt the message because only she has a (the private key). A pre-shared public key also prevents man-in-the-middle attacks.
In practice, Diffie–Hellman is not used in this way, with
being the dominant public key algorithm. This is largely for historical and commercial reasons[], namely that
created a certificate authority for key signing that became . Diffie–Hellman cannot be used to sign certificates. However, the
signature algorithms are mathematically related to it, as well as ,
component of the
protocol suite for securing
communications.
key exchange
Synonyms of Diffie–Hellman key exchange include:
Diffie–Hellman–Merkle key exchange
Diffie–Hellman key agreement
Diffie–Hellman key establishment
Diffie–Hellman key negotiation
Exponential key exchange
Diffie–Hellman protocol
Diffie–Hellman handshake
Merkle, Ralph C (April 1978). . Communications of the ACM. 21 (4): 294–299. :. Received August, 1975; revised September 1977
(PDF). . 22 (6): 644–654. :.
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Buchanan, Bill, , Bill's Security Tips
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(2nd ed.), Springer Science & Business Media, pp. 190–191,  
Barbulescu, R Gaudry, P Joux, A Thomé, Emmanuel (2014). "A Heuristic Quasi-Polynomial Algorithm for Discrete Logarithm in Finite Fields of Small Characteristic". Advances in Cryptology – EUROCRYPT 2014. Proceedings 33rd Annual International Conference on the Theory and Applications of Cryptographic Techniques. Lecture Notes in Computer Science. 8441. Copenhagen, Denmark. pp. 1–16. :.  .
C. Kaufman (Microsoft) (December 2005). . Internet Engineering Task Force (IETF).
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Gollman, Dieter (2011). Computer Security (2nd ed.). West Sussex, England: John Wiley & Sons, Ltd.  .
Williamson, Malcolm J. (January 21, 1974).
(PDF) (Technical report). Communications Electronics Security Group.
Williamson, Malcolm J. (August 10, 1976).
(PDF) (Technical report). Communications Electronics Security Group.
1987 (28K PDF file) ()
Whitfield Diffie, Proceedings of the IEEE, vol. 76, no. 5, May 1988, pp: 560–577 (1.9MB PDF file)
Boca Raton, Florida: CRC Press.  . ()
New York: Doubleday  
Martin E. Hellman, IEEE Communications Magazine, May 2002, pp:42–49. (123kB PDF file)
This article's use of
may not follow Wikipedia's policies or guidelines. Please
by removing
external links, and converting useful links where appropriate into . (March 2016) ()
, , University of Minnesota. Leading cryptography scholar
discusses the circumstances and fundamental insights of his invention of
with collaborators
at Stanford University in the mid-1970s.
– Diffie–Hellman Key Agreement Method. E. Rescorla. June 1999.
– More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE). T. Kivinen, M. Kojo, SSH Communications Security. May 2003.
(64K PDF file) ()
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