Gábor Kiss

Role of oxygen vacancy defect states in the n-type conduction of β-Ga2O3

Based on semiempirical quantum-chemical calculations, the electronic band structure of β-Ga2O3 is presented and the formation and properties of oxygen vacancies are analyzed. The equilibrium geometries and formation energies of neutral and doubly ionized vacancies were calculated. Using the calculated donor level positions of the vacancies, the high temperature n-type conduction is explained. The vacancy concentration is obtained by fitting to the experimental resistivity and electron mobility.

Fading-aware reliable and energy efficient routing in wireless sensor networks

In this paper, we introduce two fading-aware reliability based routing algorithms for wireless sensor networks (WSNs) with lossy radio links. The proposed algorithms are able to find optimal multi-hop paths in polynomial complexity, over lossy links, which are modeled by using standard fading models (e.g. Rayleigh and Rice fading). These algorithms minimize the energy consumption and ensure reliable packet transmission to the base station (BS) at the same time. A reliable path is defined in terms of successful packet transfer to the BS despite the lossy links. More precisely, the probability of correct reception of the packet at the BS must exceed a predefined threshold. The first algorithm minimizes the total energy consumption sending a packet over the selected path to the BS. On the other hand, the second algorithm selects a path which maximizes the minimum remaining energy on the node closest to exhaustion and, as a result, balances the energy consumption yielding high longevity. In both cases, reliable and energy efficient packet forwarding in WSN can be reduced to a constrained optimization problem. By using a specific link metrics, these problems can then be mapped into shortest path problems solved in polynomial time. Thus the obtained results ensure the selection of reliable paths which also guarantee minimum energy consumption in real time.

Language independent detection possibilities of depression by speech

In this study, acoustic-phonetic analysis of continuous speech and statistical analyses were performed in order to find parameters in depressed speech that show significant differences compared to a healthy reference group. Read speech materials were gathered in the Hungarian and Italian languages from both healthy people and patients diagnosed with different degrees of depression. By statistical examination it was found that there are many parameters in the speech of depressed people that show significant differences compared to a healthy reference group. Moreover, most of those parameters behave similarly in other languages such as in Italian. For classification of the healthy and depressed speech, these parameters were used as an input for the classifiers. Two classification methods were compared: Support Vector Machine (SVM) and a two-layer feed-forward neural network (NN). No difference was found between the results of the two methods when trained and tested on Hungarian language (both SVM and NN classification accuracy was 75 %). In the case of training with Hungarian and testing with Italian healthy and depressed speech both classifiers reached 77 % of accuracy.

Physiological and Cognitive Status Monitoring on the Base of Acoustic-Phonetic Speech Parameters

In this paper the development of an online monitoring system is shown in order to track physiological and cognitive condition of crew members of the Concordia Research Station in Antarctica, with specific regard to depression. Follow-up studies were carried out on recorded speech material in such a way that segmental and supra-segmental speech parameters were measured for individual researchers weakly, and the changes of these parameters were detected over time. Two kind of speech were recorded weekly by crew members in their mother tongue: a diary and a tale (“North Wind and The Sun”). An automatic language independent program was used to segment the records in phoneme level for the measurements. Such a way Concordia Speech Databases were constructed. Those acoustic-phonetic parameters were selected for the follow up study at Concordia, which parameters were statistically selected during a research on the base of the analysis of Seasonal Affective Disorder Databases gathered separately in Europe.

Computer based speech prosody teaching system

Abstract Children who are born with a profound hearing loss have no or only distorted acoustic speech target to imitate and compare their own production with. Computer based visual feedback, visual presentation of speech on screen has shown to be an effective supplement of incomplete or distorted auditory feedback in the case of children with grave hearing-impairment. In this paper, we introduce a novel prosody teaching system where intensity (accent), intonation and rhythm are presented visually for the students (in both separate and combined display mode) as visual feedback and automatic assessment scores are given jointly and separately for the goodness of intonation and rhythm. Evaluation of the automatic assessment was done with cooperation of experts in the field of treatment of hard of hearing children. The results showed that the automatic assessment scores correspond to the subjective evaluations given by the teachers. The evaluation of the whole system was done in a school for hard of hearing children, by comparing the development of a group of students using our prosody teaching system with the development of a control group. The speaking ability of students were compared by a subjective listening experiment after a 3 months teaching course. The students who used the computer based prosody teaching software could produce nicer prosody than the students in the control group.

Mono- and multi-lingual depression prediction based on speech processing

In this paper a mono- and multi-lingual study is presented about the depressed speech detection possibilities. Beck Depression Inventory questionnaires were used for the description of severity of depression of speakers for all languages. In the mono-lingual experiment a detailed speech parameter selection is shown, and the analysis of the connection between the severity of the depression and the calculated parameters is presented. The goal was to select the most relevant input feature vectors from a preselected set of vectors for the detection and prediction methods of depression. A detailed examination was carried out where and how to measure these features in continuous speech. After parameter selection, classification experiments were conducted on a Hungarian speech database. The overall accuracies of the classification experiments were 86%. The second part of this study concerns a multi-lingual automatic depression detection and prediction method, where three European languages were tested: German, Hungarian and Italian. With the selected quasi language-independent parameters, Support Vector Regression experiments were conducted on German, Hungarian and Italian speech databases, separately for both sexes. It was found that depression prediction based on speech signals can be achieved in a multi-lingual way. Our method is even capable of predicting the severity of depression in the case of a language not used during the training of the automatic prediction model. The experiments clearly show that multi-lingual depression recognition can be achieved, and it should be possible to construct an automated diagnostic tool for detecting depression, or for patient monitoring, in a multi-lingual way.

Examination of the Surface Phosphorus Content of Anodized Medical Grade Titanium Samples

In case of titanium dental implants, the main goal is to create a surface where the bone cells can attach well, therefore osseointegration can occur. The chemical composition of the surface has an important role, because the surface has a direct contact with the living tissue and induces different reactions for example peri implantitis or osseointegration. In our work titanium sample made from the most commonly used dental implant material (Ti Grade 5) were investigated. The samples were treated by chemical etching in hydrogen-chloride and in phosphoric acid to remove the cut generated burr. After that the samples were anodized in phosphoric acid solution at 10 V, 20 V, 30 V or 40 V. As a result of these treatments, titanium-dioxide layers were created on the surfaces. Phosphorus (originating from the phosphoric acid bath) may also be found on the surfaces. This may promote osseointegration. The surface compositions were investigated with the aid of Secondary Ion Mass Spectrometry (SIMS). Based on these results we can conclude that anodization in phosphoric acid solution increases the phosphorus content of the surface. Approximately to the middle of the titanium-dioxide layer the phosphorus content is constant but lower with one order of magnitude than on the surface. In the deeper layers the phosphorus content continues to decrease until the base material where it significantly reduce.

Surface analytical studies of maxillofacial implants: Influence of the preoperational treatment and the human body on the surface properties of retrieved implants

AbstractIn the present work, surface analytical investigation of unimplanted as well as retrieved pyrolytic carbon–covered carbon/carbon composite implants and Ti osteosynthesis plates is reported. The Ti plates were covered by a 200-nm-thick, anodically and thermally formed TiO2 layer. Our results suggest that although the oxide layer on the Ti miniplates remained stable during the time spent in the human body, there is still material transport between the implant and the human body. In case of the carbon/carbon composite implants, damage of the carbon fibers constituting the material was found on one side of the sterile implant and attributed to the manufacturing process. The NaCl crystals originally present on the surface of the sterile material disappeared during the time spent in the human body. As a result of the interaction with the human body, a new surface layer (mainly constituted of carbon) appeared on the implant. The results indicate that both the time spent in the human organism and the preparation of the implants before operation can have detectable effects on the investigated surface properties. Surface analytical investigations could therefore provide information not only about the biocompatibility of these materials but also about the effect of their treatment before operation.

Delay Characteristics and Server Update Optimization of Multiplayer Gaming in Mobile Environment

In this paper a novel approach to provide satisfactory multiplayer gaming quality in mobile environment is presented. The paper has two contributions: (i) evaluation of the delay characteristics of multiplayer games in mobile environment based on extensive measurements to verify whether HSDPA access can provide a satisfactory gaming quality; (ii) improving the gaming quality with new server update time optimization algorithms taking advantage of the statistical delay characteristics.