Electrical & Electronics Engineering
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ArticlePublication Open Access A 1GS/s, 9-bits DAC interleaved (2+1)-bit then 2-bit per cycle SAR ADC(Istanbul University, 2020-07) El-Sawy, Salma; Tekin, Ahmet; Electrical & Electronics Engineering; TEKİN, Ahmet; El-Sawy, SalmaThis paper presents a high speed Successive Approximation Register Analog to Digital Converter (SAR ADC) for low-noise low-power satellite transceiver applications. The system is a (2+1) then 2-bit per cycle SAR ADC of 1GS/s sampling rate, 9-bits resolution designed in a 65nm standard CMOS technology. The system resolves 9 bits with a special switching scheme in a total of 4 cycles per sample. This is achieved by interleaving 4 Capacitive Digital to Analog Converter (C-DACs) of unit capacitance 1fF. Since the interleaving is limited to the DACs only which match well, the design does not suffer from the drawbacks of full interleaving. Hence, better power efficiency and performance metrics were obtained in comparison to regular interleaved ADCs. A special timing with an extra first bit comparator is optimized to leave proper timing margins for every step from a single 4-GHz low noise clock source which is readily available in the 8- GHz direct conversion front-end. This comparator is reused as all the other active comparators in the both interleaving phases. The proposed design achieved an effective number of bits (ENOB) of 8.2 bits at Nyquist with power consumption of 12mW, resulting in a Figure of Merit (FoM) of 38.37 fJ/conversion-step.ArticlePublication Open Access 3D neuromorphic wireless power transfer and energy transmission based synaptic plasticity(IEEE, 2019) Gülbahar, Burhan; Electrical & Electronics Engineering; GÜLBAHAR, Burhan CahitEnergy consumption combined with scalability and 3D architecture is a fundamental constraint for brain-inspired computing. Neuromorphic architectures including memristive, spintronic, and floating gate metal-oxide-semiconductors achieve energy efficiency while having challenges of 3D design and integration, wiring and energy consumption problems for architectures with massive numbers of neurons and synapses. There are bottlenecks due to the integration of communication, memory, and computation tasks while keeping ultra-low energy consumption. In this paper, wireless power transmission (WPT)-based neuromorphic design and theoretical modeling are proposed to solve bottlenecks and challenges. Neuron functionalities with nonlinear activation functions and spiking, synaptic channels, and plasticity rules are designed with magneto-inductive WPT systems. Tasks of communication, computation, memory, and WPT are combined as an all-in-one solution. Numerical analysis is provided for microscale graphene coils in sub-terahertz frequencies with unique neuron design of coils on 2D circular and 3D Goldberg polyhedron substrates as a proof-of-concept satisfying nonlinear activation mechanisms and synaptic weight adaptation. Layered neuromorphic WPT network is utilized to theoretically model and numerically simulate pattern recognition solutions as a simple application of the proposed system design. Finally, open issues and challenges for realizing WPT-based neuromorphic system design are presented including experimental implementations.Conference ObjectPublication Open Access Adaptive OFDM-based acoustic underwater transmission: system design and experimental verification(IEEE, 2017) Sadeghi, Mohammad; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Sadeghi, Mohammad; Elamassie, MohammedIn this paper, we present the design and implementation of a software defined orthogonal frequency division multiplexing (OFDM)-based underwater acoustic (UWA) communication system with link adaptation. Our system implementation is based on the customized versions of National Instruments Universal Software Radio Peripheral (USRP). The modified USRPs are interfaced with hydrophone front-ends for acoustic transmission. We investigate the performance of various adaptive algorithms where both modulation order/type and power on each subcarrier are selected based on channel conditions in order to maximize throughput. The experimental in-pool test results verify the superiority of adaptive transmission.ArticlePublication Metadata only Analysis of asynchronous cognitive radio system with imperfect sensing and bursty primary user traffic(Springer Science+Business Media, 2016-03) Ercan, Ali Özer; Electrical & Electronics Engineering; ERCAN, Ali ÖzerThis paper presents a theoretical analysis of the spectrum utilization levels in a cognitive radio system. We assume that the traffic of the primary network is bursty and asynchronous with the secondary network, which performs imperfect spectrum sensing. Collisions of the primary and the secondary packets are assumed to result in increased packet error probabilities. We present primary and secondary utilization levels under optimized secondary transmission periods for varying primary traffic characteristics and secondary sensing performance levels. The results are also validated by extensive Monte Carlo simulations. We find that an asynchronous cognitive radio network with imperfect spectrum sensing is feasible when optimized transmission periods are used. The effects of primary traffic’s burst pattern and secondary sensing performance are discussed.ReviewPublication Open Access Automatic detection of attachment style in married couples through conversation analysis(Springer, 2023-05-31) Koçak, Tuğçe Melike; Dibek, B. Ç.; Polat, Esma Nafiye; Kafesçioğlu, Nilüfer; Demiroğlu, Cenk; Electrical & Electronics Engineering; Psychology; KAFESCİOĞLU, Nilüfer; DEMİROĞLU, Cenk; Koçak, Tuğçe Melike; Polat, Esma NafiyeAnalysis of couple interactions using speech processing techniques is an increasingly active multi-disciplinary field that poses challenges such as automatic relationship quality assessment and behavioral coding. Here, we focused on the prediction of individuals’ attachment style using interactions of recently married (1–15 months) couples. For low-level acoustic feature extraction, in addition to the frame-based acoustic features such as mel-frequency cepstral coefficients (MFCCs) and pitch, we used the turn-based i-vector features that are the commonly used in speaker verification systems. Sentiments, positive and negative, of the dialog turns were also automatically generated from transcribed text and used as features. Feature and score fusion algorithms were used for low-level acoustic features and text features. Even though score and feature fusion algorithms performed similar, predictions with score fusion were more consistent when couples have known each other for a longer period of time.ArticlePublication Open Access Axial charges of octet baryons in two-flavor lattice QCD(Elsevier, 2010-03-15) Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, GürayWe evaluate the strangeness-conserving NN, ΣΣ, ΞΞ, ΛΣ and the strangeness-changing ΛN, ΣN, ΛΞ, ΣΞ axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson–octet-baryon coupling constants so as to include πΞΞ, KΛΞ and KΣΞ coupling constants. We find that the axial charges have rather weak quark mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.ArticlePublication Open Access Capacity analysis of NOMA-enabled underwater VLC networks(IEEE, 2021) Elamassie, Mohammed; Bariah, L.; Uysal, Murat; Muhaidat, S.; Sofotasios, P. C.; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, MuratVisible light communication (VLC) has recently emerged as an enabling technology for high capacity underwater wireless sensor networks. Non-orthogonal multiple access (NOMA) has been also proven capable of handling a massive number of sensor nodes while increasing the sum capacity. In this paper, we consider a VLC-based underwater sensor network where a clusterhead communicates with several underwater sensor nodes based on NOMA. We derive a closed-form expression for the NOMA system capacity over underwater turbulence channels modeled by lognormal distribution. NOMA sum capacity in the absence of underwater optical turbulence is also considered as a benchmark. Our results reveal that the overall capacity of NOMA-enabled Underwater VLC networks is significantly affected by the propagation distance in underwater environments. As a result, effective wireless transmission at high and moderate spectral efficiency levels can be practically achieved in underwater environments only in the context of local area networks. Moreover, we compare the achievable capacity of NOMA system with its counterpart, i.e., orthogonal frequency division multiple access (OFDMA). Our results reveal that NOMA system is not only characterized by achieving higher sum capacity than the sum capacity of its counterpart, OFDMA system. It is also shown that the distances between sensor nodes and the clusterhead for achieving the highest sum capacity in these two multiple access systems are different.ArticlePublication Open Access Channel modelling for indoor visible light communications(Royal Society Publishing, 2020-04-17) Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, FarshadVisible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. In this paper, we present a comprehensive survey of indoor VLC channel models. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user.ArticlePublication Open Access Co-optimization of transmission maintenance scheduling and production cost minimization(MDPI, 2019-08-01) Poyrazoğlu, Göktürk; Oh, H.; Electrical & Electronics Engineering; POYRAZOĞLU, GöktürkRegular transmission maintenance is important to keep the infrastructure resilient and reliable. Delays providing on-time maintenance increase the forced outage rate of those assets, causing unexpected changes in the operating conditions and even catastrophic consequences, such as local blackouts. The current process of maintenance schedule is based on the transmission owners' choice, with the final decision of system operator about the reliability. The requests are examined on a first-come, first-served basis, which means a regular maintenance request may be rejected, delaying the tasks that should be performed. To incorporate optimization knowledge into the transmission maintenance schedule, this study focuses on the co-optimization of maintenance scheduling and the production cost minimization. The mathematical model co-optimizes generation unit commitment and line maintenance scheduling while maintaining N-1 reliability criterion. Three case studies focusing on reliability, renewable energy delivery, and service efficiency are conducted leading up to 4% production cost savings as compared to the business-as-usual approach.ArticlePublication Open Access Coagulation measurement from whole blood using vibrating optical fiber in a disposable cartridge(SPIE, 2017-11) Yaraş, Y. S.; Gündüz, A. B.; Sağlam, G.; Ölçer, S.; Civitçi, F.; Baris, İ.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen GökseninIn clinics, blood coagulation time measurements are performed using mechanical measurements with blood plasma. Such measurements are challenging to do in a lab-on-a-chip (LoC) system using a small volume of whole blood. Existing LoC systems use indirect measurement principles employing optical or electrochemical methods. We developed an LoC system using mechanical measurements with a small volume of whole blood without requiring sample preparation. The measurement is performed in a microfluidic channel where two fibers are placed inline with a small gap in between. The first fiber operates near its mechanical resonance using remote magnetic actuation and immersed in the sample. The second fiber is a pick-up fiber acting as an optical sensor. The microfluidic channel is engineered innovatively such that the blood does not block the gap between the vibrating fiber and the pick-up fiber, resulting in high signal-to-noise ratio optical output. The control plasma test results matched well with the plasma manufacturer’s datasheet. Activated-partial-thromboplastin-time tests were successfully performed also with human whole blood samples, and the method is proven to be effective. Simplicity of the cartridge design and cost of readily available materials enable a low-cost point-of-care device for blood coagulation measurements.Conference ObjectPublication Unknown Colour gamut enhancement with remote light conversion mechanism(IOP Publishing, 2018) Köseoğlu, Devrim; Sezer, Yusuf Sinan; Karslı, K.; Electrical & Electronics Engineering; KÖSEOĞLU, Devrim; Sezer, Yusuf SinanThe backlight unit spectrum of liquid crystal displays (LCD) directly affects the colour gamut. With the invention of GaN based blue light emitting diodes (LED), phosphors and quantum dots (QD) have gained considerable scientific interest due to their broad range of applications especially in lighting and display technologies. These phosphors and QDs are used to convert the blue light of the LEDs into white in general lighting. On the other hand, in display systems, they are used to generate red and green bands. There are different application methods such as on-chip and remote configurations. In this study, we concentrate on remote phosphor and QD backlight configurations where the light conversion is done away from the chips. In our display designs, we used GaN based blue LED lateral chips as an excitation source, on the other hand, light conversion layers were placed in backlight units as a thin film for the emission of green and red bands. The mixing ratios of these composite layers were arranged to match the emission spectrum of the blue LEDs and the light conversion layer to the colour filters of the LCD, so that the green, blue, and red bands efficiently widens the colour space. The results were also compared with the on-chip phosphor arrangements.ArticlePublication Open Access Comparative characterization of indoor VLC and MMW communications via ray tracing simulations(IEEE, 2023) Hosseinabadi, Fahimeh Aghaei; Eldeeb, H. B.; Bariah, L.; Muhaidat, S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Hosseinabadi, Fahimeh AghaeiThe demand for ultra-high-speed indoor wireless connectivity is ever-increasing, which poses unique challenges for the next generation wireless communication system design. This has prompted the exploration of higher frequency bands including millimeter wave (MMW) and visible light bands in addition to the conventional sub-6 GHz band. This paper provides a comprehensive comparison of the propagation channels of these frequency bands under the same indoor environment and scenarios. We adopt ray tracing techniques for site-specific channel modeling, which enables the consideration of the three-dimensional models of the indoor environment and objects inside. It allows us to take into account different frequencies, i.e., 2.4 GHz, 6 GHz, 28 GHz, 60 GHz, 100 GHz, and visible light band as well as different transmitter types, i.e., omnidirectional/directional antennas for radio frequency systems and indoor luminaries for visible light communications (VLC). For different frequencies under consideration, we obtain channel impulse responses (CIRs) and present the channel path losses for various user trajectories in indoor environments. Furthermore, we propose closed-form expressions for the cumulative distribution functions (CDFs) of received power levels for all frequency bands under consideration. Our results demonstrate that VLC channels exhibit lower path loss than that in MMW bands but higher than that of 2.4 GHz band. In addition, it is observed that VLC systems exhibit more sensitivity to shadowing and blockage effects. Our findings further indicate that the characteristics of the propagation channel are greatly influenced by the antenna type. For instance, using omnidirectional and rectangular patch antennas results in lower path loss compared to horn antennas, and this difference becomes more significant as the transmission distance decreases.ArticlePublication Open Access Connectivity considerations for mission planning of a search and rescue drone team(TÜBİTAK, 2020) Adam, Evşen Yanmaz; Electrical & Electronics Engineering; ADAM, Evşen YanmazIn this paper, we analyze the mission success performance and mission times of centralized, distributed, and hybrid path-planning methods for a drone team whose mission is to find a target and inform the ground control. We propose two methods that integrate connectivity into the search mission path decisions. We observe that even though the coverage path-planning leads to lower search times, when target connectivity is also required, schemes that incorporate end-end connectivity into path planning result in at least 50% better mission times for small communication ranges and lower number of drones. Our results also indicate that methods to efficiently allocate resources to search and communication tasks in mission-oriented drone networks need to be designed.ArticlePublication Open Access Coordinated beamforming design for multi-user multi-cell MIMO VLC networks(IEEE, 2022-06) Naser, S.; Bariah, L.; Jaafar, W.; Muhaidat, S.; Al-Qutayri, M.; Uysal, Murat; Sofotasios, P. C.; Electrical & Electronics Engineering; UYSAL, MuratInter-cell interference (ICI) and inter-user interference (IUI) constitute a major issue towards achieving the optimum spectral efficiency (SE) and energy efficiency (EE) performance in multi-cell visible light communication (VLC) networks. Hence, advanced multiple access techniques need to be leveraged in order to improve the provided service to the users of such interfering networks. To this end, the present contribution proposes the integration of coordinated beamforming (CB) with rate-splitting multiple access (RSMA) in multi-cell VLC systems. Specifically, we consider the design of beamformers for the common and private streams in a coordinated manner between different attocells, which is shown to provide efficient mitigation of the incurred interference. Additionally, the formulated optimization problem aims to minimize the sum of the mean squared error across all attocells in order to jointly determine the optimum receive filters and coordinated transmit beamformers for RSMA streams. In this context, we illustrate through extensive computer simulations, which are carried out in a realistic setup that assumes noisy channel state information acquisition, the distinct flexibility and robustness of CB-based RSMA in mitigating the incurred interference. Finally, the offered results demonstrate the superiority of CB-based RSMA in terms of achievable SE and EE performance in multi-cell VLC networks compared to the conventional CB-based space division multiple access counterpart.ArticlePublication Open Access Coverage of a shopping mall with flexible OLED-based visible light communications(The Optical Society, 2020-03-30) Chaleshtori, Z. N.; Zvanovec, S.; Ghassemlooy, Z.; Eldeeb, Hossıen Badr; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELDEEB, Hossien Badr HossienVisible light communications (VLC) can utilize light-emitting diodes (LEDs) to provide illumination and a safe and low-cost broadcasting network simultaneously. In the past decade, there has been a growing interest in using organic LEDs (OLEDs) for soft lighting and display applications in public places. Organic electronics can be mechanically flexible, thus the potential of curved OLED panels/displays devices. This paper provides unique characteristics of a flexible OLED-based VLC link in a shopping mall. We show that, for curved OLED the radiation pattern displays a symmetry, which is wider than Lambertian. A number of scenarios of VLC system with flexible OLED are analyzed. Numerical models for the delay spread and optical path loss are derived, which followed a 2-term power series model for both empty and furnished rooms. We show that using a full-circular OLED for both empty and furnished rooms offers a uniform distribution of emitted power for the same transmission link spans. The link performance using full and half-circular OLED in an empty room shows that the average optical path losses are lower by 5 and 4 dB, compared with the furnished room.ArticlePublication Open Access Crucial topics in computer architecture education and a survey of textbooks and papers(International Association of Engineers, 2020) Yıldız, A.; Gören, S.; Uğurdağ, Hasan Fatih; Aktemur, B.; Akdoğan, Taylan; Natural and Mathematical Sciences; Electrical & Electronics Engineering; UĞURDAĞ, Hasan Fatih; AKDOĞAN, TaylanWe have been teaching undergraduate computer architecture since 2012 in an unconventional way. Most undergraduate computer architecture courses are based on microprocessors, and they quickly move into advanced topics such as instruction pipelining, forwarding, branch prediction, cache, and even memory management unit. We instead spend only the last one-third of our course on these topics. The first two thirds of the course is devoted to microcontrollers, i.e., simple-minded processors with no memory hierarchy, no branch prediction, sometimes even no pipelining. Our claim is that it is very hard to truly grasp the advanced topics without full grasp of the basics. Equipped with the above approach, this article comes up with an all-inclusive list of crucial topics for computer architecture education, and it surveys 25 computer architecture textbooks as well as 38 computer architecture education papers to see how much they cover these topics. In addition to that, the article contains a concise description of the perspective of our course. One of the pillars of our course is a working CPU on FPGA. We have so far had around 600 students design their own unique CPUs using Verilog given a complete instruction set, close to 70% of them with complete success.ArticlePublication Open Access Deep Q-learning based optimization of VLC systems with dynamic time-division multiplexing(IEEE, 2020) Siddiqi, U. F.; Sait, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, MuratThe traditional method to solve nondeterministic-polynomial-time (NP)-hard optimization problems is to apply meta-heuristic algorithms. In contrast, Deep Q Learning (DQL) uses memory of experience and deep neural network (DNN) to choose steps and progress towards solving the problem. The dynamic time-division multiple access (DTDMA) scheme is a viable transmission method in visible light communication (VLC) systems. In DTDMA systems, the time-slots of the users are adjusted to maximize the spectral efficiency (SE) of the system. The users in a VLC network have different channel gains because of their physical locations, and the use of variable time-slots can improve the system performance. In this work, we propose a Markov decision process (MDP) model of the DTDMA-based VLC system. The MDP model integrates into deep Q learning (DQL) and provides information to it according to the behavior of the VLC system and the objective to maximize the SE. When we use the proposed MDP model in deep Q learning with experienced replay algorithm, we provide the light emitting diode (LED)-based transmitter an autonomy to solve the problem so it can adjust the time-slots of users using the data collected by device in the past. The proposed model includes definitions of the state, actions, and rewards based on the specific characteristics of the problem. Simulations show that the performance of the proposed DQL method can produce results that are competitive to the well-known metaheuristic algorithms, such as Simulated Annealing and Tabu search algorithms.ArticlePublication Open Access Deep reinforcement based power allocation for the max-min optimization in non-orthogonal multiple access(IEEE, 2020) Siddiqi, U. F.; Sait, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, MuratNOMA is a radio access technique that multiplexes several users over the frequency resource and provides high throughput and fairness among different users. The maximization of the minimum the data-rate, also known as max-min, is a popular approach to ensure fairness among the users. NOMA optimizes the transmission power (or power-coefficients) of the users to perform max-min. The problem is a constrained non-convex optimization for users greater than two. We propose to solve this problem using the Double Deep Q Learning (DDQL) technique, a popular method of reinforcement learning. The DDQL technique employs a Deep Q- Network to learn to choose optimal actions to optimize users' power-coefficients. The model of the Markov Decision Process (MDP) is critical to the success of the DDQL method, and helps the DQN to learn to take better actions. An MDP model is proposed in which the state consists of the power-coefficients values, data-rate of users, and vectors indicating which of the power-coefficients can be increased or decreased. An action simultaneously increases the power-coefficient of one user and reduces another user's power-coefficient by the same amount. The amount of change can be small or large. The action-space contains all possible ways to alter the values of any two users at a time. DQN consists of a convolutional layer and fully connected layers. We compared the proposed method with the sequential least squares programming and trust-region constrained algorithms and found that the proposed method can produce competitive results.ArticlePublication Open Access Depression screening from voice samples of patients affected by parkinson’s disease(S. Karger AG, 2019-05-01) Özkanca, Yasin Serdar; Öztürk, M. G.; Ekmekci, Merve Nur; Atkins, D. C.; Demiroğlu, Cenk; Ghomi, R. H.; Electrical & Electronics Engineering; DEMİROĞLU, Cenk; Özkanca, Yasin Serdar; Ekmekci, Merve NurDepression is a common mental health problem leading to significant disability worldwide. It is not only common but also commonly co-occurs with other mental and neurological illnesses. Parkinson's disease (PD) gives rise to symptoms directly impairing a person's ability to function. Early diagnosis and detection of depression can aid in treatment, but diagnosis typically requires an interview with a health provider or a structured diagnostic questionnaire. Thus, unobtrusive measures to monitor depression symptoms in daily life could have great utility in screening depression for clinical treatment. Vocal biomarkers of depression are a potentially effective method of assessing depression symptoms in daily life, which is the focus of the current research. We have a database of 921 unique PD patients and their self-assessment of whether they felt depressed or not. Voice recordings from these patients were used to extract paralinguistic features, which served as inputs to machine learning and deep learning techniques to predict depression. The results are presented here, and the limitations are discussed given the nature of the recordings which lack language content. Our models achieved accuracies as high as 0.77 in classifying depressed and nondepressed subjects accurately using their voice features and PD severity. We found depression and severity of PD had a correlation coefficient of 0.3936, providing a valuable feature when predicting depression from voice. Our results indicate a clear correlation between feeling depressed and PD severity. Voice may be an effective digital biomarker to screen for depression among PD patients.ArticlePublication Open Access Depression-level assessment from multi-lingual conversational speech data using acoustic and text features(Springer Nature, 2020-11-17) Demiroğlu, Cenk; Besirli, A.; Özkanca, Yasin Sedar; Celik, S.; Electrical & Electronics Engineering; DEMİROĞLU, Cenk; Özkanca, Yasin SedarDepression is a widespread mental health problem around the world with a significant burden on economies. Its early diagnosis and treatment are critical to reduce the costs and even save lives. One key aspect to achieve that goal is to use technology and monitor depression remotely and relatively inexpensively using automated agents. There has been numerous efforts to automatically assess depression levels using audiovisual features as well as text-analysis of conversational speech transcriptions. However, difficulty in data collection and the limited amounts of data available for research present challenges that are hampering the success of the algorithms. One of the two novel contributions in this paper is to exploit databases from multiple languages for acoustic feature selection. Since a large number of features can be extracted from speech, given the small amounts of training data available, effective data selection is critical for success. Our proposed multi-lingual method was effective at selecting better features than the baseline algorithms, which significantly improved the depression assessment accuracy. The second contribution of the paper is to extract text-based features for depression assessment and use a novel algorithm to fuse the text- and speech-based classifiers which further boosted the performance.