David Akopian

The University of Texas at San Antonio | UTSA · Department of Electrical and Computer Engineering

The Enhanced 911 (E911) mandate of the Federal Communications Commission (FCC) drives the evolution of indoor three-dimensional (3D) location/positioning services for emergency calls. Many indoor localization systems exploit location-dependent wireless signaling signatures, often called fingerprints, and machine learning techniques for position est...

Background: Hormone therapy (HT) is highly effective for nearly all breast cancer patients with hormone receptor-positive tumors, which are about 80% of all breast cancer diagnoses. Long-term use of HT reduces cancer recurrence rates and cuts the risk of mortality nearly in half during the second decade after diagnosis. Despite proven benefits, 33%...

Background: Despite major advances in tobacco control and treatment, tobacco use remains the single largest preventable cause of morbidity and mortality in the US. Smoking prevalence is highest among Texas young adults (ages 18-29), especially those with lower education and income and those living in rural areas, like Latinos. About 19.2% of Latino...

Nowadays, automated chatbots are commonly used since they easily provide essential information. While generic chatbots are essential for open-domain dialog, specific applications are better served with task-oriented dialog systems. These task-oriented dialog systems typically solve particular tasks in the application where the chatbot and user know...

Recently, human-machine digital assistants gained popularity and are commonly used in question-and-answer applications and similar consumer-supporting domains. A class of more sophisticated digital assistants (chatbots) employing more extended dialogs follows the trend. Chatbots have become increasingly popular in recent years. Nowadays, chatbot de...

One of the most elusive types of malware in recent times that pose significant challenges in the computer security system is the kernel-level rootkits. The kernel-level rootkits can hide its presence and malicious activities by modifying the kernel control flow, by hooking in the kernel space, or by manipulating the kernel objects. As kernel-level...

Background: Physicians have unparalleled access to smokers. It is estimated that over 70% of smokers visit a physician every year, which provides a powerful opportunity to promote tobacco cessation by asking about smoking behaviors and providing cessation advice and counseling to tobacco users at every visit. In general, smokers consider a physicia...

Background: Adjuvant hormonal therapy (HT) is highly effective and appropriate for nearly all women with hormone receptor-positive tumors, making such treatment the most widely prescribed therapy for patients with this type of breast cancer. Despite its proven benefits in reducing cancer recurrence and improving survival, HT adherence is suboptimal...

Finding research professionals and collaborators to address community problems continues to be a significant barrier for many local government agencies. Research collaboration between researchers from universities, industries and local government agencies can be tremendously useful to all organizations. San Antonio Research Partnership Portal is a...

Global Navigation Satellite System (GNSS) receivers are vulnerable to intentional spoofing attacks which can manipulate position, velocity, and time (PVT) measurements. Previous work has demonstrated that Time Synchronization Attacks (TSAs) can be detected and mitigated using sparse optimization techniques which reveal spoofers’ presence in inflict...

The extraction of keywords is a critical task in natural language processing and information retrieval. It has become increasingly important in a wide range of applications, from search engines and e-commerce platforms to news and social media analysis. However, the evaluation of keyword extraction methods remains a challenging task due to the dive...

Research collaboration between academic researchers from universities, organizations and government local city departments can be tremendously useful to all institutions, but these collaborations involve a wide range of skill sets, making them difficult to establish and manage. For many local government city departments, finding research profession...

Background: The successful use of hormone therapy (HT) has contributed to improved 5-year cause-specific breast cancer survival rates, and evidence shows that long-term use produces a larger reduction in recurrence and mortality, with nearly 50% reduction in breast cancer mortality during the second decade after diagnosis. Despite the proven benefi...

With the increasing use of smartphones, performance monitoring and the analysis of mobile applications (apps) are gaining momentum. Smartphones are resource-constrained devices. Thus, mobile apps typically rely on cloud services for the execution of resource-intensive functionalities, storage, and computation power. Measuring the user experience is...

The core part of the computer operating system that plays an important role in managing computer resources is the kernel. One of the most elusive types of malware in recent times that pose significant security threats on the computer operating system kernel is the kernel-level rootkit. The kernel-level rootkit can hide its presence and malicious ac...

Given how smart phones, internet services, and social media have shown great potential for assisting smoking cessation, we constructed a Facebook chat application based on our previous work with SMS texting services. This report summarizes findings from 2,364 Spanish-speaking young adults recruited through Facebook advertising in South Texas during...

TP-Link Technologies Co, Ltd. is a Chinese manufacturer of networking products and has a 42% share of the consumer WLAN market, making it the market leader. The company sells about 150 million devices per year. Many people worldwide use the Internet every day and are connected to the Internet with their computers. In the world of smart homes, even...

This paper presents a novel time synchronization attack (TSA) model for the Global Positioning System (GPS) based on clock data behavior changes in a higher-order derivative domain. Further, the time synchronization attack rejection and mitigation based on sparse domain (TSARM-S) is presented. TSAs affect stationary GPS receivers in applications wh...

BACKGROUND Quitxt is a mobile smoking cessation service delivered through text messaging (SMS) and Facebook Messenger chat. Cigarette smoking and alcohol use are well known to be concomitant behaviors, however there is a lack of studies related to recruitment of smokers for mobile cessation services at places where alcohol is consumed, such as bars...

Background: Cigarette smoking and alcohol use are well known to be concomitant behaviors, but there is a lack of studies related to recruitment of smokers for mobile cessation services at places where alcohol is consumed, such as bars and clubs. Adapting recruitment strategies to expand the reach of cessation programs to where tobacco users are lo...

p>Background: The successful use of hormone therapy (HT) has contributed to improved 5-year cause-specific breast cancer survival rates and evidence shows that long-term use produces a larger reduction in recurrence and mortality, with nearly 50% reduction in breast cancer mortality during the second decade after diagnosis. Despite the proven benef...

With the evolving artificial intelligence technology, the chatbots are becoming smarter and faster lately. Chatbots are typically available round the clock providing continuous support and services. A chatbot or a conversational agent is a program or software that can communicate using natural language with humans. The challenge of developing an in...

The core part of the operating system is the kernel, and it plays an important role in managing critical data structure resources for correct operations. The kernel-level rootkits are the most elusive type of malware that can modify the running OS kernel in order to hide its presence and perform many malicious activities such as process hiding, mod...

With the evolving artificial intelligence technology, the chatbots are becoming smarter and faster lately. Chatbots are typically available round the clock providing continuous support and services. A chatbot or a conversational agent is a program or software that can communicate using natural language with humans. The challenge of developing an in...

Background: Adjuvant hormonal therapy (HT) is highly effective and appropriate for nearly all women with hormone receptor-positive tumors, making such treatment the most widely prescribed therapy for patients with this type of breast cancer. Despite its proven benefits in reducing cancer recurrence and improving survival, HT adherence is suboptimal...

Background: Quitxt is an evidence-based mobile text messaging service for smoking cessation promoted in South Texas via social media advertising. A group analysis of 798 Quitxt participants with a mean age of 29.3 found that 21% of the enrollees reported abstinence at 7 months. This confirmed that a text and mobile media service specifically design...

This paper presents a novel time synchronization attack (TSA) model for the Global Positioning System (GPS) based on clock data behavior changes in a higher-order derivative domain. Further, TSA rejection and mitigation based on sparse domain (TSARM-S) is presented. TSAs affect stationary GPS receivers in applications where precise timing is requir...

UNSTRUCTURED Rural residents face numerous challenges in accessing quality healthcare for management of chronic diseases (e.g., obesity, diabetes), including scarcity of healthcare services and insufficient public transport. Digital health interventions, that include modalities such as internet, smart phones, and monitoring sensors, may help increa...

Unstructured: Rural residents face numerous challenges in accessing quality healthcare for management of chronic diseases (e.g., obesity, diabetes), including scarcity of healthcare services and insufficient public transport. Digital health interventions, that include modalities such as internet, smart phones, and monitoring sensors, may help incr...

This work proposes a global navigation satellite system (GNSS) spoofing detection and classification technique for single antenna receivers. We formulate an optimization problem at the baseband correlator domain by using the Least Absolute Shrinkage and Selection Operator (LASSO). We model correlator tap outputs of the received signal to form a dic...

This work proposes a global navigation satellite system (GNSS) spoofing detection and classification technique for single antenna receivers. We formulate an optimization problem at the baseband correlator domain by using the Least Absolute Shrinkage and Selection Operator (LASSO). We model correlator tap outputs of the received signal to form a dic...

While some UAVs can operate with a given degree of autonomy (e.g., path following, obstacle avoidance, auto return, and other flight modes), many civilian drones have a safety pilot standby all the time for abnormal conditions. This is typically done within lineof- sight due to regulations. While flying within line-of-sight, radio frequency communi...

Mobile health (mHealth) apps have received increasing attention, due to their abilities to support patients who suffer from various conditions. mHealth apps may be especially helpful for patients with chronic diseases, by providing pertinent information, tracking symptoms, and inspiring adherence to medication regimens. To achieve these objectives,...

Mobile Health (mHealth) applications (apps) are being widely used to monitor health of patients with chronic medical conditions with the proliferation and the increasing use of smartphones. Mobile devices have limited computation power and energy supply which may lead to either delayed alarms, shorter battery life or excessive memory usage limiting...

In South Texas, smoking rates among young Latino adults aged 18–29 are high (23.2%–25.7%). This is a serious public health problem, yet few are reached by services to help them quit smoking. Cellular phones have an extraordinary potential for assisting smoking cessation by providing access to peer modeling and social reinforcement for behavior chan...

Wi-Fi fingerprinting-based indoor localization has received increased attention due to its proven accuracy and global availability. The common received-signal-strength-based (RSS) fingerprinting presents performance degradation due to well-known signal fluctuations, but more recently, the more stable channel state information (CSI) has gained popul...

It has been a decade since smartphone application stores started allowing developers to post their own applications. This paper presents a narrative review on the state-of-the-art and the future of technology used by researchers in the field of mobile health promotion. Researchers build high cost, complex systems with the purpose of promoting healt...

Recently, location-based services (LBS) have steered attention to indoor positioning systems (IPS). WLAN-based IPSs relying on received signal strength (RSS) measurements such as fingerprinting are gaining popularity due to proven high accuracy of their results. Typically, sets of RSS measurements at selected locations from several WLAN access poin...

With the growing integration of location based services (LBS) such as GPS in mobile devices, indoor position systems (IPS) have become an important role for research. There are several IPS methods such as AOA, TOA, TDOA, which use trilateration for indoor location estimation but are generally based on line-of-sight. Other methods rely on classifica...

This paper presents the new generation of LabVIEW-based GPS receiver testbed that is based on National Instruments' (NI) LabVIEW (LV) platform in conjunction to C/C++ dynamic link libraries (DLL) used inside the platform for performance execution. This GPS receiver has been optimized for real-time operation and has been developed for fast prototypi...

The U.S. global position system (GPS) is one of the existing global navigation satellite systems (GNSS) that provides position and time information for users in civil, commercial and military backgrounds. Because of its reliance on many applications nowadays, it's crucial for GNSS receivers to have robustness to intentional or unintentional interfe...

Indoor positioning systems (IPS) are emerging technologies due to an increasing popularity and demand in location based service (LBS). Because traditional positioning systems such as GPS are limited to outdoor applications, many IPS have been proposed in literature. WLAN-based IPS are the most promising due to its proven accuracy and infrastructure...

The operation of critical infrastructures such as the electrical power grid, cellphone towers, and financial institutions relies on precise timing provided by stationary GPS receivers. These GPS devices are vulnerable to a type of spoofing called Time Synchronization Attack (TSA), whose objective is to maliciously alter the timing provided by the G...

The operation of critical infrastructures such as the electrical power grid, cellphone towers, and financial institutions relies on precise timing provided by stationary GPS receivers. These GPS devices are vulnerable to a type of spoofing called Time Synchronization Attack (TSA), whose objective is to maliciously alter the timing provided by the G...

Modern infrastructure heavily relies on various location-based services using global navigation satellite systems (GNSSs) such as the U.S. global positioning system for access to positioning, navigation, and timing information. Location information enables guidance in many applications, including finding the location of vehicles for public safety e...

[This corrects the article DOI: 10.1016/j.conctc.2018.10.001.].

Indoor positioning systems exploiting WLAN signal measurements such as Received Signal Strength (RSS) are gaining popularity due to high accuracy of the results. Sets of RSS and other measurements at designated locations from available WLAN access points (APs) are conventionally called fingerprints and retrieved from network cards at typically one...

The ubiquitousness of location based services (LBS) has proven effective for many applications such as commercial, military, and emergency responders. Software-defined radio (SDR) has emerged as an adequate framework for development and testing of global navigational satellite systems (GNSS) such as the Global Position System (GPS). SDR receivers a...

Recently, several global navigation satellite systems (GNSS) emerged following the transformative technology impact of the first GNSS: US Global Positioning System (GPS). The power level of GNSS signals as measured at the earths surface is below the noise floor and is consequently vulnerable against interference. Spoofers are smart GNSS-like interf...

Recently, several global navigation satellite systems (GNSS) emerged following the transformative technology impact of the first GNSS--U.S. global positioning system (GPS). The power level of GNSS signals as measured at earth's surface is below the noise floor and is consequently vulnerable against interference. Spoofers are smart GNSS-like interfe...

Adjuvant endocrine hormonal therapy (EHT) is highly effective and appropriate for nearly all breast cancer patients with hormone receptor-positive tumors, which represent 75% of all breast cancer diagnoses. Long-term use of EHT reduces recurrence rates and nearly halves the risk of death during the second decade after diagnosis. Despite the proven...

Indoor positioning systems exploiting wireless local area network (WLAN) signal measurements, such as received signal strength (RSS), are gaining popularity due to high accuracy of the results. Sets of RSS and other measurements at designated locations from available WLAN access points are conventionally called fingerprints and typically retrieved...

The ubiquitousness of location-based services has proven effective for many applications such as commercial, military, and emergency responders. Software-defined radio (SDR) has emerged as an adequate framework for the development and testing of global navigational satellite systems such as the global position system (GPS). SDR receivers are consta...

This paper introduces the Time Synchronization Attack Rejection and Mitigation (TSARM) technique for Time Synchronization Attacks (TSAs) over the Global Positioning System (GPS). The technique estimates the clock bias and drift of the GPS receiver along with the possible attack contrary to previous approaches. Having estimated the time instants of...

Rapidly evolving technologies like data analysis, smartphone and web-based applications, and the Internet of things have been increasingly used for healthy living, fitness and well-being. These technologies are being utilized by various research studies to reduce obesity. This paper demonstrates design and development of a dataflow protocol that in...

This paper introduces the Time Synchronization Attack Rejection and Mitigation (TSARM) technique for Time Synchronization Attacks (TSAs) over the Global Positioning System (GPS). The technique estimates the clock bias and drift of the GPS receiver along with the possible attack contrary to previous approaches. Having estimated the time instants of...

A remote laboratory gateway enables a plurality of students to access and control a laboratory experiment remotely. Access is provided by an experimentation gateway, which is configured to provide secure access to the experiment via a network-centric, web-enabled interface graphical user interface. Experimental hardware is directly controlled by an...