19 research outputs found
Cascading Randomized Weighted Majority: A New Online Ensemble Learning Algorithm
With the increasing volume of data in the world, the best approach for
learning from this data is to exploit an online learning algorithm. Online
ensemble methods are online algorithms which take advantage of an ensemble of
classifiers to predict labels of data. Prediction with expert advice is a
well-studied problem in the online ensemble learning literature. The Weighted
Majority algorithm and the randomized weighted majority (RWM) are the most
well-known solutions to this problem, aiming to converge to the best expert.
Since among some expert, the best one does not necessarily have the minimum
error in all regions of data space, defining specific regions and converging to
the best expert in each of these regions will lead to a better result. In this
paper, we aim to resolve this defect of RWM algorithms by proposing a novel
online ensemble algorithm to the problem of prediction with expert advice. We
propose a cascading version of RWM to achieve not only better experimental
results but also a better error bound for sufficiently large datasets.Comment: 15 pages, 3 figure
Multi-User Privacy Mechanism Design with Non-zero Leakage
A privacy mechanism design problem is studied through the lens of information
theory. In this work, an agent observes useful data that is
correlated with private data which is assumed to be also
accessible by the agent. Here, we consider users where user demands a
sub-vector of , denoted by . The agent wishes to disclose to
user . Since is correlated with it can not be disclosed
directly. A privacy mechanism is designed to generate disclosed data which
maximizes a linear combinations of the users utilities while satisfying a
bounded privacy constraint in terms of mutual information. In a similar work it
has been assumed that is a deterministic function of , however in
this work we let and be arbitrarily correlated. First, an upper
bound on the privacy-utility trade-off is obtained by using a specific
transformation, Functional Representation Lemma and Strong Functional
Representaion Lemma, then we show that the upper bound can be decomposed into
parallel problems. Next, lower bounds on privacy-utility trade-off are
derived using Functional Representation Lemma and Strong Functional
Representaion Lemma. The upper bound is tight within a constant and the lower
bounds assert that the disclosed data is independent of all
except one which we allocate the maximum allowed leakage to it. Finally, the
obtained bounds are studied in special cases.Comment: arXiv admin note: text overlap with arXiv:2205.04881,
arXiv:2201.0873
New Privacy Mechanism Design With Direct Access to the Private Data
The design of a statistical signal processing privacy problem is studied
where the private data is assumed to be observable. In this work, an agent
observes useful data , which is correlated with private data , and wants
to disclose the useful information to a user. A statistical privacy mechanism
is employed to generate data based on that maximizes the revealed
information about while satisfying a privacy criterion. To this end, we use
extended versions of the Functional Representation Lemma and Strong Functional
Representation Lemma and combine them with a simple observation which we call
separation technique. New lower bounds on privacy-utility trade-off are derived
and we show that they can improve the previous bounds. We study the obtained
bounds in different scenarios and compare them with previous results.Comment: arXiv admin note: substantial text overlap with arXiv:2201.08738,
arXiv:2212.1247
A Design Framework for Strongly -Private Data Disclosure
In this paper, we study a stochastic disclosure control problem using
information-theoretic methods. The useful data to be disclosed depend on
private data that should be protected. Thus, we design a privacy mechanism to
produce new data which maximizes the disclosed information about the useful
data under a strong -privacy criterion. For sufficiently small leakage,
the privacy mechanism design problem can be geometrically studied in the space
of probability distributions by a local approximation of the mutual
information. By using methods from Euclidean information geometry, the original
highly challenging optimization problem can be reduced to a problem of finding
the principal right-singular vector of a matrix, which characterizes the
optimal privacy mechanism. In two extensions we first consider a scenario where
an adversary receives a noisy version of the user's message and then we look
for a mechanism which finds based on observing , maximizing the mutual
information between and while satisfying the privacy criterion on
and under the Markov chain .Comment: 16 pages, 2 figure
Private Variable-Length Coding with Sequential Encoder
A multi-user private data compression problem is studied. A server has access
to a database of files, , each of size bits and is
connected to an encoder. The encoder is connected through an unsecured link to
a user. We assume that each file is arbitrarily correlated with a private
attribute , which is assumed to be accessible by the encoder. Moreover, an
adversary is assumed to have access to the link. The users and the encoder have
access to a shared secret key . We assume that at each time the user asks
for a file , where corresponds to the demand
vector. The goal is to design the delivered message after the user send his demands to the encoder
such that the average length of is minimized, while satisfying:
i. The message does not reveal any information about , i.e.,
and are independent, which corresponds to the perfect privacy
constraint; ii. The user is able to decode its demands, , by using
, and the shared key . Here, the encoder sequentially encode each
demand at time , using the shared key and previous encoded
messages.
We propose a variable-length coding scheme that uses privacy-aware
compression techniques. We study proposed upper and lower bounds on the average
length of in an example. Finally, we study an application
considering cache-aided networks.Comment: arXiv admin note: substantial text overlap with arXiv:2306.1318
Cache-Aided Private Variable-Length Coding with Zero and Non-Zero Leakage
A private cache-aided compression problem is studied, where a server has
access to a database of files, , each of size bits and
is connected through a shared link to users, each equipped with a local
cache of size bits. In the placement phase, the server fills the users
caches without knowing their demands, while the delivery phase takes place
after the users send their demands to the server. We assume that each file
is arbitrarily correlated with a private attribute , and an adversary
is assumed to have access to the shared link. The users and the server have
access to a shared key . The goal is to design the cache contents and the
delivered message such that the average length of is
minimized, while satisfying: i. The response does not reveal any
information about , i.e., and are independent, which
corresponds to the perfect privacy constraint; ii. User is able to decode
its demand, , by using , its local cache , and the shared
key . Since the database is correlated with , existing codes for
cache-aided delivery do not satisfy the perfect privacy condition. Indeed, we
propose a variable-length coding scheme that combines privacy-aware compression
with coded caching techniques. In particular, we use two-part code construction
and Functional Representation Lemma. Finally, we extend the results to the
case, where and can be correlated, i.e., non-zero leakage is
allowed
Private Variable-Length Coding with Zero Leakage
A private compression design problem is studied, where an encoder observes
useful data , wishes to compress it using variable length code and
communicates it through an unsecured channel. Since is correlated with
private attribute , the encoder uses a private compression mechanism to
design encoded message and sends it over the channel. An adversary is
assumed to have access to the output of the encoder, i.e., , and tries
to estimate . Furthermore, it is assumed that both encoder and decoder have
access to a shared secret key . The design goal is to encode message with minimum possible average length that satisfies a perfect privacy
constraint. To do so we first consider two different privacy mechanism design
problems and find upper bounds on the entropy of the optimizers by solving a
linear program. We use the obtained optimizers to design . In two cases
we strengthen the existing bounds: 1. ; 2. The
realization of follows a specific joint distribution. In particular,
considering the second case we use two-part construction coding to achieve the
upper bounds. Furthermore, in a numerical example we study the obtained bounds
and show that they can improve the existing results.Comment: arXiv admin note: text overlap with arXiv:2306.13184,
arXiv:2309.09034, arXiv:2211.15525, arXiv:2310.1912
Assessing Attitudes of Medical Students towards First Contact with Patient in Tehran (2016-17)
Background: Early experience of clinical arena as first situations can be effective in selection or refusing medicine as profession is so important that programmers and administrators should consider these settings as one of the most elements in educational programs.Materials and Methods: This study was a cross-sectional study and including presently studying students in medicine field of medical sciences universities. Sample size was estimated for 275 students. Participants were selected from schools of medicine: Iran University (IUMS), Shahid Beheshti University, and Islamic Azad University using stratified random sampling method. Data was collected in March of 2016 by a researcher made questionnaire determined its validity and reliability. Data was analyzed using chi-squared test, t-test, Mann-Whitney and Kruskal-Wallis test.Results: Mean score of medical students’ attitude from 15 five-degree scale questions was 51.22 ± 6.32. The mean scores of attitude in men and women were 51.37±6.16 and 51.06±6.53, respectively (p=0.687). Overall, 13.8 % of students had positive attitude towards first contact with patient, 10.5 % of students had negative attitude and 75.6 % had no opinion. The mean scores of attitude towards first contact with patient in Iran university, Shahid Beheshti university and Islamic Azad university were 50.40±5.00, 52.71±5.91 and 46.12±5.97, respectively (p<0.001). The mean scores of attitude towards first contact with patient in reformed educational system and old educational system were 52.35±5.83 and 46.12±5.97 respectively, with a significant difference between two types of educational system (p<0.001).Conclusion: As respects more positive attitude of students in reformed educational system in comparison with old educational system, special attention to courses of early contact with patient may contribute to decreasing educational insufficiency and distance between theory and practice and lead to the satisfaction all of beneficiaries
The global burden of adolescent and young adult cancer in 2019 : a systematic analysis for the Global Burden of Disease Study 2019
Background In estimating the global burden of cancer, adolescents and young adults with cancer are often overlooked, despite being a distinct subgroup with unique epidemiology, clinical care needs, and societal impact. Comprehensive estimates of the global cancer burden in adolescents and young adults (aged 15-39 years) are lacking. To address this gap, we analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, with a focus on the outcome of disability-adjusted life-years (DALYs), to inform global cancer control measures in adolescents and young adults. Methods Using the GBD 2019 methodology, international mortality data were collected from vital registration systems, verbal autopsies, and population-based cancer registry inputs modelled with mortality-to-incidence ratios (MIRs). Incidence was computed with mortality estimates and corresponding MIRs. Prevalence estimates were calculated using modelled survival and multiplied by disability weights to obtain years lived with disability (YLDs). Years of life lost (YLLs) were calculated as age-specific cancer deaths multiplied by the standard life expectancy at the age of death. The main outcome was DALYs (the sum of YLLs and YLDs). Estimates were presented globally and by Socio-demographic Index (SDI) quintiles (countries ranked and divided into five equal SDI groups), and all estimates were presented with corresponding 95% uncertainty intervals (UIs). For this analysis, we used the age range of 15-39 years to define adolescents and young adults. Findings There were 1.19 million (95% UI 1.11-1.28) incident cancer cases and 396 000 (370 000-425 000) deaths due to cancer among people aged 15-39 years worldwide in 2019. The highest age-standardised incidence rates occurred in high SDI (59.6 [54.5-65.7] per 100 000 person-years) and high-middle SDI countries (53.2 [48.8-57.9] per 100 000 person-years), while the highest age-standardised mortality rates were in low-middle SDI (14.2 [12.9-15.6] per 100 000 person-years) and middle SDI (13.6 [12.6-14.8] per 100 000 person-years) countries. In 2019, adolescent and young adult cancers contributed 23.5 million (21.9-25.2) DALYs to the global burden of disease, of which 2.7% (1.9-3.6) came from YLDs and 97.3% (96.4-98.1) from YLLs. Cancer was the fourth leading cause of death and tenth leading cause of DALYs in adolescents and young adults globally. Interpretation Adolescent and young adult cancers contributed substantially to the overall adolescent and young adult disease burden globally in 2019. These results provide new insights into the distribution and magnitude of the adolescent and young adult cancer burden around the world. With notable differences observed across SDI settings, these estimates can inform global and country-level cancer control efforts. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.Peer reviewe