210 research outputs found
Mitigation of H.264 and H.265 Video Compression for Reliable PRNU Estimation
The photo-response non-uniformity (PRNU) is a distinctive image sensor
characteristic, and an imaging device inadvertently introduces its sensor's
PRNU into all media it captures. Therefore, the PRNU can be regarded as a
camera fingerprint and used for source attribution. The imaging pipeline in a
camera, however, involves various processing steps that are detrimental to PRNU
estimation. In the context of photographic images, these challenges are
successfully addressed and the method for estimating a sensor's PRNU pattern is
well established. However, various additional challenges related to generation
of videos remain largely untackled. With this perspective, this work introduces
methods to mitigate disruptive effects of widely deployed H.264 and H.265 video
compression standards on PRNU estimation. Our approach involves an intervention
in the decoding process to eliminate a filtering procedure applied at the
decoder to reduce blockiness. It also utilizes decoding parameters to develop a
weighting scheme and adjust the contribution of video frames at the macroblock
level to PRNU estimation process. Results obtained on videos captured by 28
cameras show that our approach increases the PRNU matching metric up to more
than five times over the conventional estimation method tailored for photos
Oblivious data hiding : a practical approach
This dissertation presents an in-depth study of oblivious data hiding with the emphasis on quantization based schemes. Three main issues are specifically addressed:
1. Theoretical and practical aspects of embedder-detector design.
2. Performance evaluation, and analysis of performance vs. complexity tradeoffs.
3. Some application specific implementations.
A communications framework based on channel adaptive encoding and channel independent decoding is proposed and interpreted in terms of oblivious data hiding problem. The duality between the suggested encoding-decoding scheme and practical embedding-detection schemes are examined. With this perspective, a formal treatment of the processing employed in quantization based hiding methods is presented. In accordance with these results, the key aspects of embedder-detector design problem for practical methods are laid out, and various embedding-detection schemes are compared in terms of probability of error, normalized correlation, and hiding rate performance merits assuming AWGN attack scenarios and using mean squared error distortion measure.
The performance-complexity tradeoffs available for large and small embedding signal size (availability of high bandwidth and limitation of low bandwidth) cases are examined and some novel insights are offered. A new codeword generation scheme is proposed to enhance the performance of low-bandwidth applications. Embeddingdetection schemes are devised for watermarking application of data hiding, where robustness against the attacks is the main concern rather than the hiding rate or payload. In particular, cropping-resampling and lossy compression types of noninvertible attacks are considered in this dissertation work
Source Camera Verification from Strongly Stabilized Videos
Image stabilization performed during imaging and/or post-processing poses one
of the most significant challenges to photo-response non-uniformity based
source camera attribution from videos. When performed digitally, stabilization
involves cropping, warping, and inpainting of video frames to eliminate
unwanted camera motion. Hence, successful attribution requires the inversion of
these transformations in a blind manner. To address this challenge, we
introduce a source camera verification method for videos that takes into
account the spatially variant nature of stabilization transformations and
assumes a larger degree of freedom in their search. Our method identifies
transformations at a sub-frame level, incorporates a number of constraints to
validate their correctness, and offers computational flexibility in the search
for the correct transformation. The method also adopts a holistic approach in
countering disruptive effects of other video generation steps, such as video
coding and downsizing, for more reliable attribution. Tests performed on one
public and two custom datasets show that the proposed method is able to verify
the source of 23-30% of all videos that underwent stronger stabilization,
depending on computation load, without a significant impact on false
attribution
Kosova Türklerinin siyasal örgütlenme girişimleri : Kosova Demokratik Türk Partisi
Bu çalışmada “Kosova Türklerinin Siyasi Örgütlenme Girişimleri: Kosova Demokratik Türk Partisi konulu çalışma inşacı kuram çerçevesinde ele alınmıştır. Konunun anlaşılabilirliği açısından Kosova’nın kısa bir tarihi arka planı çizilerek, ülkenin geçtiği üç önemli dönemi; Tito dönemi, Miloşeviç dönemi ve uluslararası toplum vesayeti altında dönemde yaşanan gelişmelere dikkat çekilmiştir. Bunu takiben, tarihsel süreç içerisinde Türk toplumunun varlık mücadelesi, örgütlenme girişimleri, hukuki statüsü ve gelişen olaylara karşı duruşu, söylemi ve mücadeleleri ele alınmıştır. Bu çerçevede, Türk toplumunun varlığını etkileyen önemli gelişmeler nice ki; baskı politikaları, yönetim değişiklikleri, sayımlar, göç olgusu ve devletin azınlık politikaları da irdelenerek, bunların Türk toplumuna etkisi ve Türk toplumunun bunlara refleksleri yansıtılmaya çalışılmıştır. Çalışmada ayrıca, Doğru Yol Derneğinden başlayarak, Türk Demokratik Birliği’nin kuruluşu, Kosova Demokratik Türk Partisine dönüşümü, bölünmesi ve diğer partilerin kurulması konuları üzerinde durulmuştur. Bunun dışında tezin ana aktörü olan, Kosova Demokratik Türk Partisinin ülkenin iç ve dış politikadaki gelişmelere yaklaşımı, söylemi ve eylemleri de örneklerle açıklanarak, çizmeye çalıştığı devletçi politikası örneklerle yansıtılmaya çalışılmıştır. Türk toplumunun ülkede düzenlenen yerel ve genel seçimlere katılımları çerçevesinde seçim platformları, seçim çalışmaları ve seçim sonuçları da karşılaştırılarak, elde edilen başarı ve başarısızlıkların altı çizilmiştir. Seçim sonuçlarından sonra toplumun temsiliyeti ve temsilcilerin yaptıkları çalışmalara da yer verilen çalışmada Türk toplumun geleceği için birlik ver beraberliğin taşıdığı önemin de altı çizilmiştir.This study is heavily based on “Political organization initiatives of Kosovo Turks: Kosovo Democratic Turkish Party” is adrressed within the constructivist theoretical framework. In terms of comprehensibleness of the study, Kosovo`s short historical backgroung is considered in the three important period that is passed by the country: Tito era, Milosevic era and International Community custody emerging developements during the period. Following this, the existential struggle of turkish society, organizational initiatives, their legal status and po sition, attitude towards the facts, statements and struggles are adressed within historical process. In this context, important developements affecting the existence of Turkish society like: repression policies, governing varieties,census, migration fact and state minority policies and it`s effects to the Turkish society and the reflects of Turkish society were examined and tried to be reflected. This study also considers the establishment of Turkish Democratic Union, it`s transformation to Kosovo Democratic Turkish Party, it`s dislocation and establishment of the other parties starting from the Right Path Association. Except this, study will review approaches of the Kosovo Democratic Turkish Party which is main character of the thesis, against States domestic and foreign policy developments, discourses and actions were also explained with examples including the statist policy too. The achievements and failures of the Turkish society are highlighted by comparing election platforms, election practices and election results within the framework of participation level in local and general elections held in the country. Then by the election results, through showing the society representativeness and their mission, study emphasizes the importance of the unity and solidarity for the future of Kosovo Turks
Makarnal ı k Buğdayda Triticum durum Desf. Gama I şini ve EMS'nin Farkl ı Dozları n ı n Klorofil Mutasyonları n ı n Oluşumu Üzerine Etkileri
lslah programlar ı n ı n temel hedefi verimi yüksek makarnal ı k buğday Triticum durum Desf. çeşitlerini geliştirmektir. Islah programlar ı mevcut olan çeşitliliğ i art ı rmay ı ve genetik varyasyonu zenginle ştirmeyi amaçlar. Genetik varyasyon mutasyon yoluyla art ı r ı labilir. Bitki ı slah ı n ı n önemli bir sorunu uygun mutagenik muamelenin seçimidir. Bu çal ışman ı n amac ı , makarnal ı k buğday çeş itlerinin mutagenlere duyarl ı l ığı n ı Mı bitkilerinin fertilitesi ve M2 bitkilerinde klorofil mutasyonlar ı n ı belirleyerek saptamakt ı r. Bu çal ışma 1996 ve 1997 y ı llar ı nda Tokat-Kazova şartları nda yürütülmüştür. Araşt ı rmada bitki materyali olarak Gediz-75 ve Sofu makarnal ı k buğday çeş itleri kullan ı lm ışt ı r. Kobalt 60 6°Co kaynağı ndan elde edilen gama i şini tohumlar ı fiziksel mutagen ve EMS kimyasal mutagen olarak uygulanm ışt ı r. EMS uygulamas ı ön ı slatma yap ı lmadan 8 saat oda s ı cakl ığı nda yap ı lm ış ve uygulama süresi sonunda tohumlar 6 saat süreyle y ı kanm ışt ı r. Tohumlar 50 Gy, 100 Gy, 150 Gy ve 200 Gy gama ışı n ı ile ışı nlanm ış ve % 0.1, % 0.2, % 0.3, % 0.4 EMS ile muamele edilmi ştir. Mutagenlerin uyguland ığı çeşitler ayr ı ayrı denemeye al ı nm ışt ı r. Ayr ı ca, gama i şini ve EMS uygulamaları birbirinden ayr ı olarak "Tesadüf Bloklar ı Deneme Deseni"nde 3 tekerrürlü olarak kurulmu ştur. Araşt ı rma sonuçlar ı na göre, MIbitkilerinin fertilitesi EMS uygulamas ı yla karşı laşt ı r ı ld ığı zaman gamma i şini uygulamas ı nda daha düşük ç ı km ışt ı r. Mutasyon spektrumu ve frekans ı muamelerle ve çeşitlere bağl ı olarak değ işmiştir. Mutagenlerin etkileri yüksek dozlarda belirgin bir şekilde artm ışt ı r. En yüksek mutagenik verim Gediz-75 çe şidinde % 0.4 EMS dozundan, Sofu çe şidinde ise 100 Gy gama ışı n' dozundan elde edilmi ştir
Security issues in watermarking applications - a deeper look
Although it is clear that security is an important issue in digital watermarking applications, the main concerns ad-dressed by the current literature are robustness, capacity and imperceptibility. The inadequacy of the prevailing de-sign paradigm in tackling security issues is mainly due to an incomplete assessment of the threat model. The goal of this paper is to take a detailed and rigorous look at the threat model for a variety of watermarking applications. In this extended abstract, we outline the security requirements for a few common watermarking applications and explore in more detail the threat model for a specific application that involves establishing ownership of multimedia content
Ten years after ImageNet: a 360° perspective on artificial intelligence
It is 10 years since neural networks made their spectacular
comeback. Prompted by this anniversary, we take a holistic
perspective on artificial intelligence (AI). Supervised learning for
cognitive tasks is effectively solved—provided we have enough
high-quality labelled data. However, deep neural network
models are not easily interpretable, and thus the debate between
blackbox and whitebox modelling has come to the fore. The rise
of attention networks, self-supervised learning, generative
modelling and graph neural networks has widened the
application space of AI. Deep learning has also propelled the
return of reinforcement learning as a core building block of
autonomous decision-making systems. The possible harms made
possible by new AI technologies have raised socio-technical
issues such as transparency, fairness and accountability. The
dominance of AI by Big Tech who control talent, computing
resources, and most importantly, data may lead to an extreme
AI divide. Despite the recent dramatic and unexpected success
in AI-driven conversational agents, progress in much-heralded
flagship projects like self-driving vehicles remains elusive. Care
must be taken to moderate the rhetoric surrounding the field
and align engineering progress with scientific principles
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