Abstract: Our previous research findings suggested this integrated study in order to monitor changes of bone properties and assess bone integrity using vibrational characteristics in osteoporosis. Method is based on measurement of bone dynamic characteristic (Modal Damping Factor - MDF). Experimental animal model was ovariectomized rat followed by alendronate treatment. According to experimental design, adult female Wistar rats were ovariectomized and 60 days later, with confirmed osteoporosis, the population was divided in two groups. One was administered alendronate and the second was given no treatment. Furthermore, established techniques, such as pQCT, Bone Biochemical Markers and Histomorphometry were applied at all time points, in order to compare and correlate to MDF. Results obtained indicated the induction of osteoporosis due to ovariectomy and rendered MDF capable of monitoring changes in bone material properties and architecture, with high sensitivity and repeatability.
Abstract: Materials subjected to alternating stresses
exhibit temperature fluctuations indicative of damping.
Temperature effects give rise to entropy
production. An analysis is made to obtain the entropy
produced for a vibration cycle. This corresponds to
the reciprocity of temperature rise and strain yielded
that alter the material damping factor as a function of
shape and magnitude of material porosity. Prototype
bars of pure aluminum oxide with different porosity
are considered. They consist of uniformly distributed
cavities and are subjected to alternating axial stress.
Dynamic characteristics of the porous medium are
determined to evaluate the damping factor of the
tested bars. The experimental data correlate well with
the analytical results. The damping factor measured
and calculated in this work, can be used as an
indicator of structural integrity.
Abstract: The contemporary methods for the assessment of the quality of human mandible, in order to facilitate the decision making for dental implants, include bone density measurements through dual-energy X-Ray absorptiometry (DEXA) or its variations. The estimation of mandible quality with these methods is related to subjectivity, comparability and reliability problems, which results in restricted capability of secure assessment of bone quality. Monitoring of loss of structural integrity is applied in this work through modal analysis, in order to obtain an objective assessment of mandible bone quality. Specifically, modal damping factor (MDF) and bone mineral density (BMD) measurements are performed on human cadaveric mandibles. From the data acquired clearly arises a very promising correlation between MDF and BMD, reinforcing the belief from our previous research findings that this method can lead to a mandible quality assessment tool, thus encouraging further research investigation.
Abstract: Osteoporosis is a metabolic bone disease characterized by reduced bone mass and deterioration of bone microarchitecture. It results from the shift of the osteoblast-osteoclast activity equilibrium in favor of the later. Although, a number of biochemical markers, such as collagen I N-telopeptide (NTx) and osteocalcin (OC), have been used for monitoring bone remodeling, a new, monitoring, non-invasive method, which is based on the measurement of the dynamic characteristic of bone and is known as modal damping factor (MDF), has not been evaluated as a diagnostic tool for osteoporosis. Bisphosphonates, such as alendronate, have an established role in the treatment of osteoporosis. The aim of the present study was, therefore, to evaluate the effects of alendronate on the levels of MDF, serum NTx and OC on osteoporosis induced by ovariectomy in rats. Furthermore, the effects of alendronate on osteoporosis have been histologically evaluated. Fifteen adult female Wistar rats were bilaterally ovariectomized and osteoporosis was histologically confirmed and by the use of peripheral quantitative computerized tomography (pQCT). MDF was applied to assess the bone structural integrity. The serum levels of NTx (37.4 +/- 0.5 nM bone collagen equivalents, BCE) and OC (111.0 +/- 8.2 ng/mL) were found to significantly increase, following ovariectomy (72.0 +/- 2.9 nM BCE and 213.5 +/- 12.1 ng/mL, respectively, p < 0.001). As assessed by histology and the levels of NTx and OC in sera, animals treated with alendronate presented a statistically significant deceleration in the progression of the disease in comparison to the no-therapy control group (alendronate group NTx levels: 146.3 +/- 8.9 nM BCE versus no-therapy control group NTx levels: 265.3 +/- 14.0 nM BCE, p < 0.001, alendronate group OC levels: 205.6 +/- 18.2 ng/mL versus no-therapy group OC levels: 353.9 +/- 26.1 ng/mL, p < 0.001). Data obtained from the vibration analysis performed illustrated that the change in damping was equal or greater to the change in total and trabecular density, respectively. Damping increased with decreasing bone density, as expected, given that damping accounts for the structural integrity of bone (MDF value before ovariectomy: 0.058 +/- 0.003 versus MDF value after ovariectomy: 0.098 +/- 0.003, p < 0.001). The higher damping values correspond to more deteriorated structures. In particular, both total and trabecular density were significantly decreased following ovariectomy (total density before ovariectomy: 702.4 +/- 19.0 versus total density after ovariectomy: 542.2 +/- 12.8, p < 0.001, trabecular density before ovariectomy: 445.3 +/- 13.0 versus trabecular density after ovariectomy: 396.7 +/- 18.4, p < 0.05). MDF value of the alendronate group (0.07 +/- 0.002) was significantly lower (p < 0.001) as compared to MDF value after ovariectomy (0.098 +/- 0.003) and that of the no-therapy group (0.1 +/- 0.004, p < 0.001). The administration of alendronate seemed to have no effect on either total or trabecular density, since both parameters continued to decrease (alendronate group total density: 549.4 +/- 12.3, alendronate group trabecular density: 368.4 +/- 14.7). However, when this was compared to the no-therapy group, a statistically significant difference of total density at the 0.05 level was observed (no-therapy total density: 464.8 +/- 9.1). The results of this study suggest that combined measurements of MDF, NTx and OC may be a potential diagnostic tool for osteoporosis and monitoring bone integrity during treatment with bisphosphonates. Furthermore, administration of alendronate showed to offer a critical deceleration in the progression of osteoporosis. (c) 2006 Elsevier B.V. All rights reserved.
Abstract: The role of leptin during the progression of osteoporosis was investigated in ovariectomized rats by correlation of serum leptin levels with N-telopeptide of collagen type I (NTx) and osteocalcin levels before ovariectomy and 20, 40 and 60 days after the operation. Furthermore, peripheral quantitative computed tomography was used to confirm the development of severe osteoporosis in rats on day 60. The levels of NTx and osteocalcin were significantly increased on day 20 [61.9 +/- 5.4 nM BCE (bone collagen equivalents) and 215.6 +/- 53.3 ng/ mL respectively] in comparison to those before ovariectomy (41.3 +/- 1.7 nM BCE and 60.4 +/- 10.9 ng/ mL). Accordingly, leptin was significantly elevated on day 20 (3033 +/- 661 vs. 606 +/- 346 pg/mL before ovariectomy). Bone markers and leptin levels remained constant up to day 40, while a slight, but not statistically significant, decrease was noted for osteocalcin and leptin on day 60. Although leptin and bone markers did not correlate before ovariectomy (r = 0.09 for NTx and r = -0.05 for osteocalcin), strong correlation was observed at all time points after ovariectomy. The data obtained suggest that the alterations in serum leptin levels during the progression of osteoporosis in ovariectomized rats follow the alterations in bone markers.
Abstract: We applied a noninvasive method to assess bone structural integrity. The method is based
on the measurement of the dynamic characteristics of the bone (quality factor and modal
damping factor) by applying vibration excitation in the range of acoustic frequencies, in
the form of an acoustic sweep signal. Excised sheep femora were tested to detect changes
in modal damping, density (kg/m3), bone mineral density (kg/m2) and bone mineral (hydroxyapatite)
percentage. The changes were recorded after each time of chemical treatment
of the bones performed to gradually cause mineral removal, thus simulating osteoporosis.
It was shown that the change in quality factor and damping was in all cases
on average equal or greater to the change in all other measured characteristics, thus
strengthening the potential of the proposed method to become a valuable assessment tool
for monitoring bone integrity and osteoporosis.
Abstract: To examine the hypothesis that the glans penis acts protectively, absorbing forces, during coitus. Five potent patients (mean age 46.8 +/- 9.7 y), who had indication for surgical excision of the glans for penile carcinoma were included in the present study. Intraoperatively, intracavernosal pressure (ICP) was adjusted by saline infusion and maintained by a pressure feedback infusion pump to a pressure value of 70 mmHg. Using a dynamometer, an external compressive force of 0.5 kg was applied at the glans penis and the changes in ICP were monitored. Measurements were repeated after surgical excision of the glans. Significant ICP changes were noticed in all patients after excision of the glans. Mean preoperative ICP was 161 +/- 11.5 mmHg, while after glansectomy it reached 206.6 +/- 13 mmHg. DeltaICP was 45.8 +/- 10.57 mmHg. Two of the patients' partners reported pain during intercourse postoperatively, possibly due to the impact of the force applied by the rigid corpora cavernosa on the anterior vaginal wall without any absorption by the glans. The glans penis restricts the increase in ICP during sexual intercourse, playing a protective role for both the corpora cavernosa and the female genitalia.
Abstract: When a material is subjected to an alternating stress field there are temperature fluctuations throughout its volume due to thermoelastic effect. The resulting irreversible heat conduction leads to entropy production, which in turn is the cause for thermodynamic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping factor as a function of shape and magnitude of existing crack in the structure. A homogeneous, isotropic, elastic bar of orthogonal shape is considered with a single-edge crack under alternating uniform axial stress. The analytical determination of the dynamic characteristics of the cracked structure yielded the damping factor of the bar, the material damping factor and a good correlation of depth of crack with the damping factor. Experimental results on cracked bars are in good correlation with the analysis. (C) 2001 Academic Press.
Abstract: The objective of this work is to use artificial neural networks (ANN) for the long-term performance prediction of thermosiphonic type solar domestic water heating (SDWH) systems. Thirty SDWH systems have been tested and modelled according to the procedures outlined in the standard ISO 9459-2 at three locations in Greece. From these, data from 27 of the systems were used for training and testing the network while data from the remaining three were used for validation. Two ANNs have been trained using the monthly data produced by the modeling program supplied with the standard ISO 9459-2. Different networks were used depending on the nature of the required output, which is different in each case. The first network was trained to estimate the solar energy output of the system for a draw-off quantity equal to the storage tank capacity(at the end of the solar energy collection period) and the second one was trained to estimate the solar energy output of the system and the average quantity of hot water per month at demand temperatures of 35 and 40 degrees C. The collector areas of the considered systems were varying between 1.81 m(2) and 4.38 m(2). Open and closed thermosiphonic systems have been considered both with horizontal and vertical storage tanks. In this way the networks were trained to accept and handle a number of unusual cases. The input data in both networks are similar to the ones used in the program supplied with the standard. These were the size and performance characteristics of each system and various climatic data. In the second network the demand temperature was also used as input. For the first network the statistical coefficient of multiple determination (R-2-value) obtained for the training data set was equal to 0.9993. For the second network the R-2-value for the two output parameters was equal to 0.9848 and 0.9926, respectively. Unknown data were subsequently used to investigate the accuracy of prediction and R-2-values equal to 0.9913 for the first network and 0.9733 and 0.9940 for the second were obtained. These results indicate that the proposed method can successfully be used for the prediction of the solar energy output of the system for a draw-off equal to the volume of the storage tank or for the solar energy output of the system and the average quantity of the hot water per month for the two demand water temperatures considered. (C) 2000 Elsevier Science Ltd. All rights reserved.
Abstract: When a material is subjected to alternating stresses, there are temperature fluctuations indicative of damping. Temperature effects give rise to entropy production. An analysis is made to obtain the entropy produced for a vibration cycle. This corresponds to the reciprocity of temperature rise and strain yielded that alter the material damping factor (MDF) as a function of shape and magnitude of material porosity or existing cracks. A homogeneous, isotropic, elastic bar is considered. It consists of uniformly distributed cavities or a single-edge crack subjected to alternating axial stresses. Dynamic characteristics of the porous or cracked medium are determined to evaluate the damping factor of the bar and/or of the material. The experimental data correlate well with the analytical results. The calculated damping factor in this work can be used as an indicator of structural integrity. (C) 2000 Elsevier Science Ltd. All rights reserved.
Abstract: An expert system capable of learning from the electric car operation is used to evaluate the drive train performance and energy management and furthermore, monitor faults. This system using the computational power of modern portable personal computers, user friendly data input and output, and full-screen editor capabilities is used for on-board drive train monitoring, energy management optimization, and fault diagnosis.
Abstract: Artificial Neural Networks (ANN) are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. They can learn from examples, are fault tolerant, are able to deal with non-linear problems, and once trained can perform prediction at high speed. ANNs have been used in diverse applications and they have shown to be particularly effective in system modelling as well as for system identification. The objective of this work is to train an artificial neural network (ANN) to learn to predict the performance of a thermosiphon solar domestic water heating system. This performance is measured in terms of the useful energy extracted and of the stored water temperature rise. An ANN has been trained using performance data for four types of systems, all employing the same collector panel under varying weather conditions. In this way the network was trained to accept and handle a number of unusual cases. The data presented as input were, the storage tank heat loss coefficient (U-value), the type of system (open or closed), the storage volume, and a total of fifty-four readings from real experiments of total daily solar radiation, total daily diffuse radiation, ambient air temperature, and the water temperature in storage tank at the beginning of the day. The network output is the useful energy extracted from the system and the water temperature rise. The statistical coefficient of multiple determination (R-2-value) obtained for the training data set was equal to 0.9914 and 0.9808 for the two output parameters respectively. Both values are satisfactory because the closer R-2-value is to unity the better is the mapping. Unknown data for all four systems were subsequently used to investigate the accuracy of prediction. These include performance data for the systems considered for the training of the network at different weather conditions. Predictions with maximum deviations of 1 MJ and 2.2 degrees C were obtained respectively. Random data were also used both with the performance equations obtained from the experimental measurements and with the artificial neural network to predict the above two parameters. The predicted values thus obtained were very comparable. These results indicate that the proposed method call successfully be used for the estimation of the performance of the particular thermosiphon system at ally of the different types of configuration used here. The greatest advantage of the present model is the capacity of the network to learn from examples and thus gradually improve its performance. This is done by embedding experimental knowledge in the network. (C) 1999 Elsevier Science Ltd. All rights reserved.
Abstract: Artificial Neural Networks (ANN) are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. They can be trained to predict results from examples, are fault tolerant, are able to deal with non-linear problems, and once trained can perform prediction at high speed. ANNs have been used in diverse applications and they have shown to be particularly useful in system modeling and for system identification. The objective of this work was to train an ANN to learn to predict the useful energy extracted and the temperature rise in the stored water of solar domestic water heating (SDHW) systems with the minimum of input data. An ANN has been trained based on 30 known cases of systems, varying from collector areas between 1.81 m(2) and 4.38 m(2). Open and closed systems have been considered both with horizontal and vertical storage tanks. In addition to the above, an attempt was made to consider a large variety of weather conditions. In this way the network was trained to accept and handle a number of unusual cases. The data presented as input were the collector area, storage tank heat loss coefficient (U-value), tank type, storage volume, type of system, and ten readings from real experiments of total daily solar radiation, mean ambient air temperature, and the water temperature in the storage tank at the beginning of a day. The network output is the useful energy extracted from the system and the temperature rise in the stored water. The statistical R-2-value obtained for the training data set was equal to 0.9722 and 0.9751 for the two output parameters respectively. Unknown data were subsequently used to investigate the accuracy of prediction. These include systems considered for the training of the network at different weather conditions and completely unknown systems. Predictions within 7.1% and 9.7% were obtained respectively. These results indicate that the proposed method can successfully be used for the estimation of the useful energy extracted from the system and the temperature rise in the stored water. The advantages of this approach compared to the conventional algorithmic methods are the speed, the simplicity, and the capacity of the network to learn from examples. This is done by embedding experiential knowledge in the network. Additionally, actual weather data have been used for the training of the network, which leads to more realistic results as compared to other modeling programs, which rely on TMY data that are not necessarily similar to the actual environment in which a system operates. (C) 1999 Elsevier Science Ltd. All rights reserved.
Abstract: We developed a noninvasive method to evaluate bone structural integrity. It is based on the measurement of the dynamic characteristics of the bone using sweeping sound excitation in the range of acoustic frequencies. The Quality Factor (a measure of material damping) has been used as an indicator of the tendency of the bone to fracture. Results of animal studies have supported this hypothesis since linear correlations were observed between bone density, quality factor, and impact strength. A vibration excitation in the form of an acoustic sweep signal is applied to a bone to measure the quality factor. Rat hones were tested, obtained from animals with osteoporosis age-dependent (tested in vitro) or ovariectomy-induced (tested in vivo), and compared with bones of healthy (control) rats. The change in damping was, on average, equal or greater to the change in density. Moreover, excellent correlation of the quality factor was obtained with bone fracture energy measured with an impact test. During a vibration cycle, the changing strain results in temperature changes due to the reciprocity of temperature and strain. Nonreversible conduction of heat due to the unequal temperature change results in entropy production that is enhanced due to the stress concentration about the voids associated with bone porosity. Damping is a measure of the production of entropy. Its measure, the quality factor represents a potentially useful tool for monitoring bone integrity, which is deteriorating in diseases characterized by disruption of the trabecular architecture, such as osteoporosis. A computational model yielded results that are in good correlation with the experimental results.
Abstract: Computing the value of the Jacobian elliptic functions, given the argument u and the parameter m, is a problem, whose solution can be found either tabulated in tables of elliptic functions [1] or by use of existing software, such as Mathematica, etc. The inverse problem, finding the argument, given the:Jacobian elliptic function and the parameter tn, is a problem whose solution is found only in tables of elliptic functions. Standard polynomial inverse interpolation procedures fail, due to ill conditioning of the system of the unknowns. In this paper, we describe a numerical procedure based on the convergence of the unknowns of the solution, by the use of arithmetical method, as an alternative way of solving the problem. The method gives very good results with no significant error, in the computation of the argument of the Jacobian elliptic function given the Jacobian elliptic function and the parameter. This new procedure is important in problems involving cavities or inclusions of ellipsoidal shape encountered in the mechanical design of bearings, filters, and composite materials. They are also important in the modeling of porosity of bones. This porosity may lead to osteoporosis, a disease which affects bone mineral density in humans with bad consequences. Also these procedures are of importance in problems encountered in the physics discipline such as in the analysis of the dependence of the maximum tunneling current on external magnetic field for large area Josephson junctions with overlap boundary conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.
Abstract: Design of electric cars faces a significant growth all over the world. Powered by rechargeable batteries these vehicles can contribute significantly to the reduction of the big cities' pollution. The shape of the vehicle in our times is of major importance for the market and it represents the car's philosophy and character. Stylling requires the definition of the general dimensions and layout of the car in advance. Computer aided techniques were developed to support a systematic design process of E-240, a 2400 mm long electric mini-car, developed at the University of Patras.
Abstract: When a material is subjected to an alternating stress field, there are temperature fluctuations throughout its volume due to the thermoelastic effect. The resulting irreversible heat conduction leads to entropy production that in turn is the cause of thermoelastic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping factor as a function of the porosity of the material. A homogeneous, isotropic, elastic bar of cylindrical shape is consider ed with uniformly distributed spherical cavities under alternating uniform axial stress. The analytical calculation of the dynamic characteristics of the porous structure yielded the damping factor of the bar and the material damping factor Experimental results on porous metals are in good correlation with an analysis.
Abstract: When a material is subjected to an alternating stress field, there are temperature fluctuations throughout its volume due to thermoelastic effects. The resulting irreversible heat conduction leads to entropy production which, in turn, is the cause of thermodynamic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping factor as a function of shape and magnitude of the porosity of the material. A homogeneous, isotropic, elastic bar of cylindrical shape is considered with uniformly distributed ellipsoidal cavities under alternating uniform axial stress. The analytical calculation of the dynamic characteristics of the porous structure yielded the change of the material damping factor as a function of shape and magnitude of the porosity of the material. A homogeneous, isotropic, elastic bar of cylindrical shape is considered with uniformly distributed ellipsoidal cavities under alternating uniform axial stress. The analytical calculation of the dynamic characteristics of the porous structure yielded the damping factor of the bar and the material damping factor. Experimental results on porous metals are in good correlation with analysis. (C) 1997 Academic Press Limited.
Abstract: The aim of this article is the study of the application of expert systems to a mechanical engineering research domain with practical and commercial interest, such as design and manufacturing of Solar Domestic Hot Water (SDHW) Systems. The issues studied were the selection and the design of SDHW systems. The application of an expert system was explored. Frame and class formalism was used for knowledge representation together with forward and backward chaining techniques for drawing conclusions and utilizing the accumulated information present. The appropriate computer program was developed to yield the selection of SDHW systems using the software tool LEONARDO 3.0 (1989), an integrated environment for the development of expert systems. The developed program was tested with data according to the Greek standard ELOT corresponding to the ISO/DIS 9459-2 and it performed successfully for 21 SDHW systems available on the Greek market. Apart from the possibility of selection of a SDHW system, the program also supports the facility for updating its knowledge base with new data so that it can be adapted to changes appearing on the market. The program proved to be functional and user friendly to a high degree. Copyright (C) 1996 Elsevier Science Ltd.
Abstract: Computing the value of the Jacobian elliptic functions, given the argument mu and the parameter m, is a problem, whose solution can be found either tabulated in tables of elliptic functions [1] or by use of existing software, such as Mathematica, etc. The inverse problem, finding the argument, given the Jacobian elliptic function and the parameter m, is a problem whose solution is found only in tables of elliptic functions. Standard polynomial inverse interpolation procedures fail, due to ill conditioning of the system of linear equations of the unknowns. In this paper, we describe a numerical procedure for inverse interpolation which gives good results in the computation of the argument of the Jacobian elliptic function given the Jacobian elliptic function and the parameter. Also, a direct interpolation is described which gives the Zeta function of Jacobi and the complete elliptic integral of the second kind given the argument and the parameter. These new interpolation procedures are important in problems involving cavities or inclusions of ellipsoidal shape encountered in the mechanical design of bearings, filters and composite materials. They are also important in the modelling of porosity of bones. This porosity may lead to osteoporosis, a disease which affects bone mineral density in humans with bad consequences.
Abstract: The increasing environmental pollution, the noise emitions, the deteriorating traffic conditions, in the big cities, and the decreasing oil deposits have forced the car industries to search for alternative energy sources and new concepts. Increasing R&D efforts in the field of the electric vehicle, which seems to become a substantial part of the fleet of automobiles in the years to come, request for automated and simplified design and simulation techniques. The design of the chassis of E-240, a two seated electric compact city car, developed at the University of Patras with the use of computer aided software tools, is presented here.
