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内容概要:本文针对犯罪团伙的识别问题,提出了多种数学建模方法。利用已知的消息流量数据,通过三个优先级列表(模型1、模型2和模型3)来确定潜在的共谋者及其可能的领导角色。具体来说,模型1综合了可疑消息的数量和其他相关因素;模型2引入了全概率定律计算节点成为共谋者的概率;模型3则基于图论的概念,考虑了最短路径和关系的紧密度。最终,模型4通过中心性的概念提名三位主要嫌疑人:Paul、Elsie 和 Dolores(高级经理)。此外,还探讨了这些模型在其他领域的应用潜力,如生物医学中的细胞感染识别。 适合人群:对数据分析、图论和犯罪分析感兴趣的研究人员、数据科学家和技术专家。 使用场景及目标:主要用于执法部门在打击商业欺诈和团伙犯罪时,快速识别潜在共谋者及其领导者,提高案件侦破效率。 其他说明:文中提出的方法不仅适用于犯罪团伙的识别,在其他涉及网络分析的问题上也有广泛应用前景。
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For office use only
T1 ________________
T2 ________________
T3 ________________
T4 ________________
Team Control Number
13215
Problem Chosen
C
For office use only
F1 ________________
F2 ________________
F3 ________________
F4 ________________
2012 Mathematical Contest in Modeling (MCM) Summary Sheet
(Attach a copy of this page to each copy of your solution paper.)
Type a summary of your results on this page. Do not include
the name of your school, advisor, or team members on this page.
Message Network Modeling for Crime Busting
Abstract
A particularly popular and challenging problem in crime analysis is to identify
the conspirators through analysis of message networks. In this paper, using the data of
message traffic, we model to prioritize the likelihood of one’s being conspirator, and
nominate the probable conspiracy leaders.
We note a fact that any conspirator has at least one message communication with
other conspirators, and assume that sending or receiving a message has the same
effect, and then develop Model 1, 2 and 3 to make a priority list respectively and
Model 4 to nominate the conspiracy leader.
In Model 1, we take the amount of one’s suspicious messages and one’s all
messages with known conspirators into account, and define a simple composite index
to measure the likelihood of one’s being conspirator.
Then, considering probability relevance of all nodes, we develop Model 2 based
on Law of Total Probability. In this model, probability of one’s being conspirator is
the weight sum of probabilities of others directly linking to it. And we develop
Algorithm 1 to calculate probabilities of all the network nodes as direct calculation is
infeasible.
Besides, in order to better quantify one’s relationship to the known conspirators,
we develop Model 3, which brings in the concept “shortest path” of graph theory to
create an indicator evaluating the likelihood of one’s being conspirator which can be
calculated through Algorithm 2.
As a result, we compare three priority lists and conclude that the overall rankings
are similar but quite changes appear in some nodes. Additionally, when altering the
given information, we find that the priority list just changes slightly except for a few
nodes, so that we validate the models’ stability.
Afterwards, by using Freeman’s centrality method, we develop Model 4 to
nominate three most probable leaders: Paul, Elsie, Dolores (senior manager).
What’s more, we make some remarks about the models and discuss what could
be done to enhance them in the future work. In addition, we further explain
Investigation EZ through text and semantic network analysis, so to illustrate the
models’ capacity of applying to more complicated cases. Finally, we briefly state the
application of our models in other disciplines.
Team#13215Pageof 18
1
Introduction
ICM is investigating a conspiracy whose members all work for the same noted
company which majors in developing and marketing computer software for banks and
credit card companies. Conspirators commit crimes by embezzling funds from the
company and using internet fraud to steal funds from credit cards. It is a kind of
commercial fraud. Fraud is a human endeavor, involving deception, purposeful intent,
intensity of desire, risk of apprehension, violation of trust, rationalization, etc.
Psychological factors influence the behaviors of fraud perpetrators (Sridhar
Ramamoorti, 2008).
ICM provides us the following information that they have mastered
●All 83 office workers’ names;
●15 short descriptions of the topics ( Topic 7, 11, and 13 have been deemed to be
suspicious);
●400 links of the nodes that transmit messages and the topic code numbers;
●7 known conspirators: Jean, Alex, Elsie, Paul, Ulf, Yao, and Harvey;
●8 known non-conspirators: Darlene, Tran, Jia, Ellin, Gard, Chris, Paige and
Este;
●Jerome, Delores, and Gretchen are the senior managers of the company.
For crime busting, we develop models to
●Identify all conspirators as accurately as possible, make a priority list that
shows the likelihood of one’s being conspirator, so that erroneous judgments or
miss-judgments won’t happen easily;
● Nominate the conspiracy leader.
Declaration of the given data
●“Topics.xls” contains only 15 topics, but “topic 18” appears in line 215 of
“Messages.xls”. To fix this error, we decide to neglect this invalid data and delete it.
●In page 5, line 2 of “2012_ICM_Problem.pdf”, it says that “Elsie” is one of the
known conspirators. However we find two “Elsie” with node number “7” and “37”.
Throughout some basic statistics about the message traffic containing suspicious
topics, it appears that “7 Elsie” is more likely to be a known conspirator rather than
“37 Elsie”. Therefore, we assume that “Elsie” in “2012_ICM_Problem.pdf” indicates
“Elsie” with node number 7 in “names.xls”.
●As the problem paper point out, “Delores” is a senior manager. But “Delores”
can’t be found in “names.xls” while “Dolores” is found. So we consider it as
misspelling and replace “Delores” with “Dolores”.
●“Gretchen” is also one of the senior managers. But two “Gretchen” are found in
“names.xls” with different node number “4” and “32”. In consideration of this
redundancy, we determine to pick out node 32 for “Gretchen” indicated in the
problem paper artificially. In addition, our basic statistics also shows that “32
Gretchen” has more message exchanges than “4 Gretchen”, which may imply that “32
Gretchen” is more probably the senior manager than “4 Gretchen” due to managers
often contact others more than ordinary office workers.
Team#13215Pageof 18
2
Problem analysis and assumption
Commercial fraud is committed by those intelligent people who are confident
with their professional skills. Meanwhile, this kind of crime couldn’t involve only one
person, but always need cooperation of a whole group. Thus, communication with
other conspirators would be inevitable. However, they obviously know that they are
linked together and if one person discloses their secrets, none of them can get off. So
they are conscious when they communicate with their colleagues who aren’t their
companions, especially when they talk about sensitive issues. And the higher
intellectual level of perpetrators with rich society experience, the more conscious they
are (Zhigang Lin,2010). And ICM can figure out suspicious topic which stands a good
chance of being related to the conspiracy by some content analysis method. On the
one hand, although Conspirators would try to avoid involving suspicious topics in
their messages, they have to convey this kind of information sometimes due to the
business or other reason. On the other hand, trust and close relationship play an
important role in a conspiracy group, so normal messages exchanges can also reflect
the conspiracy relationship.
Based on psychology analysis above, we can state that all conspirators have at
least one message communication with other conspirators, whether suspicious or
unsuspicious message.
In addition, we make the assumption that sending and receiving messages have
same effect when we evaluate the likelihood of one’s being conspirator;
Models
Model 1
Establishment of model
According to the analysis of the problem, the likelihood of one’s being
conspirator is related to various factors, such as what topics are contained in the
worker messages, how many messages and suspicious messages are the worker
related with, who did the worker contact with, etc. To evaluate the likelihood of one’s
being conspirators, we use the following equation which combines two quantity
indexes:
12
12
1
, 0,1, 2,...,82
2max{ } max{ }
ii
i
ii
ii
nn
pi
nn
⎛⎞
⎜⎟
=+=
⎜⎟
⎝⎠
(1)
Where is the suspicious message number that office worker sent or received
and is message number that office worker
i
sent to or received by known
conspirators.
1i
n
i
i
2
n
In order to get each value of and , we make data statistics and draw
Figure 1:
1i
n
2i
n
Team#13215Pageof 18
3
Figure. 1
Result and analysis
Figure 1 shows all the values of and . Using equation (1) we have put
forward, we can easily calculate all the values of
1i
n
2i
n
i
p
and make a priority list as Table
1 (note that
i
p
is not a probability but a metric to evaluate the likelihood, though it
value is between 0 and 1)
Table 1
No node p No node p No node p No node p
1
21
1 21 30 0.1534 43 1 0.0909 57 72 0.0313
2
67
0.9091 21 33 0.1534 44 60 0.0767 57 75 0.0313
3
54
0.6761 21 35 0.1534 44 69 0.0767 57 78 0.0313
4
7
0.6307 21 44 0.1534 44 82 0.0767 57 79 0.0313
5
43
0.4915 21 46 0.1534 47 5 0.0625 68 26 0
6
18
0.429 27 6 0.1392 47 8 0.0625 68 52 0
7
49
0.3835 27 19 0.1392 47 9 0.0625 68 53 0
8 81 0.3381 27 37 0.1392 47 11 0.0625 68 55 0
9 48 0.321 27 38 0.1392 47 40 0.0625 68 58 0
10 3 0.2784 27 41 0.1392 47 42 0.0625 68 59 0
10 10 0.2784 27 50 0.1392 47 80 0.0625 68 61 0
12 20 0.2756
33 0 0.1364 54 25 0.0455 68 62 0
13 2 0.2159 34 15 0.125 54 66 0.0455 68 63 0
13 34 0.2159 34 22 0.125 54 73 0.0455 68 64 0
15 16 0.2017 36 14 0.1222 57 12 0.0313 68 68 0
15 17 0.2017 36 45 0.1222 57 23 0.0313 68 70 0
17 28 0.1705 38 31 0.108 57 24 0.0313 68 71 0
17 47 0.1705 38 36 0.108 57 39 0.0313 68 74 0
19 4 0.1563 38 65 0.108 57 51 0.0313 68 76 0
19 13 0.1563 41 29 0.0938 57 56 0.0313 68 77 0
21 27 0.1534 41 32 0.0938 57 57 0.0313
As shown in Table 1, all the known conspirators (heavy tape and red mark) are
ranked in the very front of the list, which indicates the model is effective to some
extent that it can recognize some workers who is most likely to be conspirators.
However, some non-conspirators (green mark and Italic type) are also up at the front,
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