Hellenic Army Academy

Vári, Greece

Hellenic Army Academy

Vári, Greece

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Volos C.K.,Hellenic Army Academy | Kyprianidis I.M.,Aristotle University of Thessaloniki | Stouboulos I.N.,Aristotle University of Thessaloniki
Signal Processing | Year: 2013

This paper presents a novel image encryption scheme, which uses a chaotic True Random Bits Generator (TRBG). The chaotic TRBG is based on the coexistence of two different synchronization phenomena. The first one is the well-known complete chaotic synchronization while the second one is a recently new proposed synchronization phenomenon, the inverse π-lag synchronization. This coexistence is observed in the case of two mutually coupled identical nonlinear circuits. The nonlinear circuit, which is used, produces double-scroll chaotic attractors. The initial conditions of the coupled system and the values of the circuit's parameters serve as the private key of the proposed cryptographic scheme. In order to face the challenge of using this chaotic TRBG in such cryptographic schemes, the produced bits sequence is subjected to statistical tests which are the well-known Federal Information Processing Standards-140-2. This bits sequence has then been used to encrypt and decrypt gray-scale images. Also, the security analysis of the encrypted image demonstrates the high security of the proposed encryption scheme. © 2012 Elsevier B.V. All rights reserved.


Volos Ch.K.,Hellenic Army Academy | Kyprianidis I.M.,Aristotle University of Thessaloniki | Stouboulos I.N.,Aristotle University of Thessaloniki
Robotics and Autonomous Systems | Year: 2013

In many autonomous mobile robotic missions the complete and fast coverage of the workspace, scanned by an unpredictable trajectory, plays a crucial role. To satisfy these special demands in the design of an autonomous mobile robot, a motion controller, based on the dynamical behavior of a known discrete chaotic system, the Logistic map, is presented in this paper. The proposed method is based on a microcontroller for realizing a chaotic random bit generator and converting the produced chaotic bit sequence, to the robot's trajectory of motion. The experimental results confirm that this approach, with an appropriate sensor for obstacle avoidance, can obtain very satisfactory results in regard to the fast scanning of the robot's workspace with unpredictable way. © 2013 Elsevier B.V. All rights reserved.


Volos C.K.,Hellenic Army Academy | Kyprianidis I.M.,Aristotle University of Thessaloniki | Stouboulos I.N.,Aristotle University of Thessaloniki
Robotics and Autonomous Systems | Year: 2012

This work presents a chaotic path planning generator which is used in autonomous mobile robots, in order to cover a terrain. The proposed generator is based on a nonlinear circuit, which shows chaotic behavior. The bit sequence, produced by the chaotic generator, is converted to a sequence of planned positions, which satisfies the requirements for unpredictability and fast scanning of the entire terrain. The nonlinear circuit and the trajectory-planner are described thoroughly. Simulation tests confirm that with the proposed path planning generator better results can be obtained with regard to previous works. © 2012 Elsevier B.V. All rights reserved.


Nikolaidis P.T.,Hellenic Army Academy
Central European Journal of Medicine | Year: 2012

The objectives of this study were to examine (a) the prevalence of overweight/obesity, (b) the relationship between body mass index (BMI) and body fat percent (BF), and (c) the association between BMI, BF and power output in adult male soccer players. Members of competitive soccer clubs (n=169, aged 22.7±4.2yr) were examined for anthropometric characteristics and body composition, and performed the physical working capacity in heart rate 170 min-1 test (PWC170), a force-velocity test (F-v) and the Wingate anaerobic test (WAnT). Based on international BMI cut-off points, 17.8% (n=30) of participants were classified as overweight. BMI was correlated with BF (r=0.67, p<0.001) and could be predicted based on the equation BF=1.193 BMI-12.24 (standard error of estimate 2.49). BMI and BF were in inverse relationship with mean power during WAnT (r=-0.30, p<0.001; r=-0.47, p<0.001, respectively). BF was also in inverse relationship with PWC170 (r=-0.26, p<0.001) and maximal power of the F-v test (r=-0.18, p=0.020).The prevalence of overweight among participants was lower than what is observed in general population. The findings confirmed previous observations on general population about the negative effect of overweight and fatness on selected parameters of physical fitness. © Versita Sp. z o.o.


Stefanatos D.,Hellenic Army Academy
Automatica | Year: 2016

Optomechanical cooling is a prerequisite for many exotic applications promised by modern quantum technology and it is crucial to achieve it in short times, to minimize the undesirable effects of the environment. We formulate cavity optomechanical cooling as a minimum-time optimal control problem on anti-de Sitter space of appropriate dimension and use the Legendre pseudospectral optimization method to estimate the minimum time and the corresponding optimal control, for various values of the maximum coupling rate between the cavity field and the mechanical resonator. This framework can also be applied for the fast creation of optomechanical entanglement and to improve the efficiency of an optomechanical quantum heat engine. © 2016 Elsevier Ltd


Havenetidis K.,Hellenic Army Academy
Journal of the Royal Army Medical Corps | Year: 2016

Introduction Creatine is considered an effective nutritional ergogenic aid to enhance exercise performance. In spite of the publication of several reviews in the last decade on the topic of exercise performance/sports and creatine there is a need for an update related to the military given the lack of information in this area. The aim of this study was to critically assess original research addressing the use of creatine supplements in the military. Methods A search of the electronic databases PubMed and SPORTDiscus, for the following key words: military personnel, trainees, recruit, soldier, physical fitness, physical conditioning, creatine supplementation, creatine ingestion, nutritional supplements to identify surveys and randomised clinical trials from journal articles and technical reports investigating the effect of creatine supplementation on military populations. Results Thirty-three out of 90 articles examined the use of creatine as a dietary supplement in military personnel. Twenty-one studies were finally selected on the basis of stated inclusion criteria for military surveys and randomised clinical trials. Most of the surveys (15/17) in the military indicate a high popularity of creatine (average 27%) among supplement users. In contrast, in most of the exercise protocols used (6/9) during randomised clinical trials creatine has produced a non-significant performance-enhancing effect. Conclusions Creatine is one of the most widely used supplemental compounds in the military. It is not considered a doping infraction or related to any adverse health effects but its long-term usage needs further investigation. Experimental research suggests that creatine supplementation does not enhance physical performance in the military. However, limitations in creatine dosage, military fitness testing and sample group selection might have underestimated the ergogenic properties of creatine. Recent studies also indicate positive effects on various aspects of total force fitness such as cognitive-psychomotor performance, bone health, musculoskeletal damage and neuromuscular function. © 2016, BMJ Publishing Group. All rights reserved.


Nikolaidis P.T.,Hellenic Army Academy
Journal of Research in Medical Sciences | Year: 2013

Background: The objectives of this study were to examine (a) the prevalence of overweight/obesity, and (b) the relationship between body mass index (BMI), body fat percentage (BF) and physical fitness in adolescent and adult female volleyball players. Materials and Methods: Adolescent (n = 102, aged 15.2 ± 2.0 year) and adult (n = 57, 25.9 ± 5.0 year) players were examined for anthropometric characteristics and body composition, and performed the physical working capacity in heart rate 170 min-1 test, a force-velocity test, the Wingate anaerobic test (WAnT), sit-and-reach test (SAR), handgrip strength test (HST) and countermovement vertical jump (CVJ). Results: Based on international BMI cut-off points, 27.5% (n = 28) of adolescent and 12.3% (n = 7) of adult participants were classified as overweight, with the prevalence of overweight being higher in girls than in women (χ2 = 4.90, P = 0.027). BMI was correlated with BF in both age groups (r = 0.72, P < 0.001 in girls; r = 0.75, P < 0.001 in women). Normal participants had superior certain physical and physiological characteristics than those who were overweight. For instance, normal girls and women had higher mean power during WAnT than their overweight counterparts (P = 0.003 and P = 0.009 respectively). Except for flexibility, BMI and BF were inversely related with physical fitness (e.g., BMI vs. HST r = -0.39, P < 0.001 in girls; BF vs. CVJ r = -0.45, P < 0.001 in women). Conclusion: The findings confirmed the negative effect of overweight and fatness on selected parameters of physical fitness. The prevalence of overweight in adolescent volleyball players was higher than in general population, which was a novel finding, suggesting that proper exercise interventions should be developed to target the excess of body mass in youth volleyball clubs.


Nikolaidis P.T.,Hellenic Army Academy
Biomedical Journal | Year: 2015

Background: Although maximal heart rate (HR max) is widely used to assess exercise intensity in sport training, and particularly in soccer, there are limited data with regards to the use of age-based prediction equations of HR max in soccer players. The aim of this study was to compare the measured-HR max with two prediction equations (Fox-HR max = 220 - age and Tanaka-HR max = 208 - 0.7 × age) in soccer players. Methods: Adolescent (n = 162, 15.8 ± 1.5 years) and adult players (n = 158, 23.4 ± 4.6 years), all members of competitive clubs, voluntarily performed a graded exercise field test (Conconi protocol) to assess HR max. Results: The measured-HR max (197.6 ± 9.4 bpm in total, 200.2 ± 7.9 bpm in adolescent players, and 195.0 ± 10.0 bpm in adult players) was explained by the formula HR max = 212.3 - 0.75 × age (r = -0.41, standard error of the estimate = 8.6). In the total sample, Fox-HR max overestimated measured-HR max [mean difference (95% confidence intervals) = 2.8 bpm (1.6; 3.9)], while Tanaka-HR max underestimated HR max [-3.3 bpm (-4.5; -2.2)]. In adolescents, Fox-HR max overestimated measured-HR max [4.0 bpm (2.5; 5.5)] and Tanaka-HR max underestimated HR max [- 3.2 bpm (-4.7; -1.8)]. In adults, Tanaka-HR max underestimated HR max [-5.0 bpm (-5.3; -4.7)], while there was not any difference between Fox-HR max and measured-HR max [1.6 bpm (-3.4; 0.2)]. Conclusions: The results of this study failed to validate two widely used prediction equations in a large sample of soccer players, indicating the need for a sport-specific equation. On the other hand, the new equation that we presented should be investigated further by future studies before being adopted by coaches and fitness trainers.


While there is a direct relationship between maximal anaerobic power (Pmax) and swimming performance, the relationship between upper and lower limbs with regard to Pmax and force-velocity (F-v) characteristics is not clear. The aim of the present study was to examine the effect of age and sex on the ratios of mechanical characteristics between upper and lower extremities of adolescent swimmers. Seventeen girls (aged 14.7±1.8 yr) (mean±standard deviation) and 28 boys (14.6±1.4 yr), all members of competitive swimming clubs, performed a F-v test for both legs and arms. In legs, boys had higher values of Pmax (t 43=2.4, p<0.05), Pmax expressed in relative to body mass values (rPmax, t 43=3.4, p<0.01) and v 0 (t 43=4.3, p<0.001), while no differences were found for F 0 (t 43=1.0, p=0.31) and v 0/F 0 (t 43=0.55, p=0.59). In arms, boys had higher values of Pmax (t 43=3.2, p<0.01), rPmax (t 43=3.9, p<0.001) and v 0 (t 43=3.4, p<0.01), while no differences were found for F 0 (t 43=1.9, p=0.06) and v 0/F 0 (t 43=0.16, p=0.87). However, no sex difference was found with regard to the ratios of Pmax (t 43=1.9, p=0.06), F 0 (t 43=1.2, p=0.23) and v 0 (t 43=1.3, p=0.20) between upper and lower extremities. There was direct relationship between age and Pmax of legs (r=0.64, p<0.01 in girls; r=0.43, p<0.05 in boys) and arms (r=0.56, p<0.05; r=0.57, p<0.01 respectively), while there was not any significant association between age and the ratios of mechanical characteristics of upper and lower limbs. These findings emphasize the need for separate evaluation of arms' and legs' force-velocity characteristics on a regular basis and the consideration of these measures in training design.


Objectives: The exploration of variability in exercise behaviour is crucial in childhood and adolescence, as a tracking of this behaviour from that chronological period to adulthood, has been annotated. Therefore, aim of this research was to investigate the familial genetic and environmental determinants of individual differences with respect to exercise participation. Equipment and methods: Six hundred and ten members (156 mothers, 140 fathers, 156 daughters and 158 sons) of 175 nuclear families completed a 16-item questionnaire of physical activity. Their trait under examination, calculated as minutes of exercise per week, was adjusted for the effect of age (age, age 2, age 3) for each gender subcategories (mothers-daughters, fathers-sons). Results: The ANOVA results (F[174,433] = 2.36, P<0.05) indicated that there was 2.36 times more variance between than within families in exercise participation, suggesting that this trait aggregated in families. Maximal heritability was estimated 0.60, that was genetic factors and shared familial environment explained the 60% of the variance in exercise levels of the participants. Conclusion: The lower correlation between spouses (r=0.21, P<0.05), with respect to other intrafamilial correlations (r=0.30, P<0.05 between parent and offspring and r=0.36, P<0.05 in siblings), highlighted the genetic factor in exercise participation. Also, the significant influence (40%) of the non-shared environment was confirmed. © 2010 Elsevier Masson SAS.

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