Pub Date : 2006-03-06DOI: 10.1163/157404006777491936
G. Maroulis
We report static dipole polarizability and hyperpolarizability values difluoroacetylene obtained from finite-field density functional theory and conventional ab initio calculations with especially designed flexible basis sets of Gaussian-type functions. Our results show that electron correlation has a small effect on the dipole polarizability but a strong one on the hyperpolarizability. The widely used B3LYP method yields molecular properties fairly close to the ab initio ones. The effect of the fluorination on the molecular properties is quite obvious at the self-consistent field level of theory: α (FCCCCF) α (HCCCCF) α (HCCCCH) and γ (FCCCCF) γ (HCCCCF) γ (HCCCCH).
{"title":"On the Electric Dipole (hyper)polarizability of Difluorodiacetylene (F-C≡C-C≡C-F)","authors":"G. Maroulis","doi":"10.1163/157404006777491936","DOIUrl":"https://doi.org/10.1163/157404006777491936","url":null,"abstract":"We report static dipole polarizability and hyperpolarizability values difluoroacetylene obtained from finite-field density functional theory and conventional ab initio calculations with especially designed flexible basis sets of Gaussian-type functions. Our results show that electron correlation has a small effect on the dipole polarizability but a strong one on the hyperpolarizability. The widely used B3LYP method yields molecular properties fairly close to the ab initio ones. The effect of the fluorination on the molecular properties is quite obvious at the self-consistent field level of theory: α (FCCCCF) α (HCCCCF) α (HCCCCH) and γ (FCCCCF) γ (HCCCCF) γ (HCCCCH).","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82445912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-03-06DOI: 10.1163/157404006777491981
V. Oliker
In this paper the problem of synthesis of offset shaped single reflector antenna is considered. This problem has to be solved when a reflector antenna system is required to control the field amplitude and/or phase on the far-field or on the output aperture in the near-field. Achieving high efficiency is a very important objective of the design and shaped reflector antennas are used for that purpose.The equations of the problem are strongly nonlinear partial differential equations which can not be analyzed by standard techniques. Though the problem has been the subject of study by many authors for over 40 years, up until recently, there were no rigorous theoretical results resolving completely the questions of existence and uniqueness. With few exceptions, authors have attacked the problem with heuristic numerical procedures, and, depending on the specific formulation, obtained different results not always in agreement with each other.In this paper a new method for solving the single reflector problem is presented. The new method allows a complete and mathematically rigorous investigation of this problem. Furthermore, the proposed method lends itself to a numerical implementation and we present here several examples.
{"title":"A Rigorous Method for Synthesis of Offset Shaped Reflector Antennas","authors":"V. Oliker","doi":"10.1163/157404006777491981","DOIUrl":"https://doi.org/10.1163/157404006777491981","url":null,"abstract":"In this paper the problem of synthesis of offset shaped single reflector antenna is considered. This problem has to be solved when a reflector antenna system is required to control the field amplitude and/or phase on the far-field or on the output aperture in the near-field. Achieving high efficiency is a very important objective of the design and shaped reflector antennas are used for that purpose.The equations of the problem are strongly nonlinear partial differential equations which can not be analyzed by standard techniques. Though the problem has been the subject of study by many authors for over 40 years, up until recently, there were no rigorous theoretical results resolving completely the questions of existence and uniqueness. With few exceptions, authors have attacked the problem with heuristic numerical procedures, and, depending on the specific formulation, obtained different results not always in agreement with each other.In this paper a new method for solving the single reflector problem is presented. The new method allows a complete and mathematically rigorous investigation of this problem. Furthermore, the proposed method lends itself to a numerical implementation and we present here several examples.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91130797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-03-06DOI: 10.1163/157404006777491909
H. Michail, A. Kakarountas, A. Milidonis, C. Goutis
Hash functions are utilized in the security layer of every communication protocol and in signature authentication schemes for electronic transactions. As time passes more sophisticated applications arise that address to more users-clients and thus demand for higher throughput. Furthermore, due to the tendency of the market to minimize devices size and increase their autonomy to make them portable, power issues should also be taken into consideration. Long rumored and now official, the popular and widely used SHA-1 hashing algorithm has been attacked successfully by researchers in China and the US. It is obvious that sometime in the near future the demand for more secure hash functions will arise but these hash functions should also fulfill industry's expectations as long as the throughput, the area and the power of these new implementations are concerned. In this paper, an implementation of SHA-256 is presented in which the achieved throughput exceeds the limit of 2 Gbps. Furthermore, power dissipation is kept low in such way that the proposed implementation can be characterized as low-power.
{"title":"Efficient FPGA Implementation of Novel Cryptographic Hashing Core","authors":"H. Michail, A. Kakarountas, A. Milidonis, C. Goutis","doi":"10.1163/157404006777491909","DOIUrl":"https://doi.org/10.1163/157404006777491909","url":null,"abstract":"Hash functions are utilized in the security layer of every communication protocol and in signature authentication schemes for electronic transactions. As time passes more sophisticated applications arise that address to more users-clients and thus demand for higher throughput. Furthermore, due to the tendency of the market to minimize devices size and increase their autonomy to make them portable, power issues should also be taken into consideration. Long rumored and now official, the popular and widely used SHA-1 hashing algorithm has been attacked successfully by researchers in China and the US. It is obvious that sometime in the near future the demand for more secure hash functions will arise but these hash functions should also fulfill industry's expectations as long as the throughput, the area and the power of these new implementations are concerned. In this paper, an implementation of SHA-256 is presented in which the achieved throughput exceeds the limit of 2 Gbps. Furthermore, power dissipation is kept low in such way that the proposed implementation can be characterized as low-power.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81048310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-03-06DOI: 10.1163/157404006778330852
G. Maroulis
We present a systematic study of the dipole polarizability of n-octane. Our investigation relies on the recently proposed minimally polarized basis sets (MinPOL). It is shown that these small basis sets yield values for the mean and the anisotropy of the polarizability convincingly close to the available experimental results.
{"title":"Static Dipole Polarizability of N-Octane Calculated With MinPol Basis Sets","authors":"G. Maroulis","doi":"10.1163/157404006778330852","DOIUrl":"https://doi.org/10.1163/157404006778330852","url":null,"abstract":"We present a systematic study of the dipole polarizability of n-octane. Our investigation relies on the recently proposed minimally polarized basis sets (MinPOL). It is shown that these small basis sets yield values for the mean and the anisotropy of the polarizability convincingly close to the available experimental results.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81574879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-03-06DOI: 10.1163/157404006779194079
M. Urban, V. Kellö
In this paper we discuss relatively routine Douglas–Kroll–Hess spin–free relativistic calculations as a tool for understanding some trends of molecular properties within the series of related molecules. Electron correlation effects are considered by the Coupled Cluster method with iterative treatment of the single and double excitation operators and perturbative treatment of triples, CCSD(T). For our analysis we use accumulated data on relativistic effects on ionization potentials, electron affinities and polarizabilities of the coinage elements, Cu, Ag, and Au and related series like Ia and IIa group elements. Next we analyze electric properties of diatomic molecules as CuF, AgF, and AuF, and compare electric properties and bonding energies of these molecules with intermetalics CuAl, AgAl, AuAl. Electric dipole moments and dipole polarizabilities of the series of oxides including a heavy atom, GeO, SnO, and PbO in their 1Σ ground states are also analyzed. Particular attention is paid to the dissociation energy of PbO and its electron affinity. The bonding character of the MeL series of complexes (Me=Cu, Ag, Au; L=H2O, NH3, and H2S) is explained by stressing the importance of the charge transfer from the lone pair of the ligand to the metal element. Relativistic effects which affect the Me electron affinity and polarizability facilitate understanding the trends of Me interactions with different ligands. We also mention using of the optimized virtual orbital space (OVOS) as an instrument which allows to circumvent problems with proper contraction needed for a specific approximate relativistic Hamiltonian. OVOS allows to reduce the computer time of correlated relativistic calculation by an order of magnitude.
{"title":"Relativistic and Electron Correlation Effects as a Tool for Explaining Some Trends in Molecular Properties and Interactions","authors":"M. Urban, V. Kellö","doi":"10.1163/157404006779194079","DOIUrl":"https://doi.org/10.1163/157404006779194079","url":null,"abstract":"In this paper we discuss relatively routine Douglas–Kroll–Hess spin–free relativistic calculations as a tool for understanding some trends of molecular properties within the series of related molecules. Electron correlation effects are considered by the Coupled Cluster method with iterative treatment of the single and double excitation operators and perturbative treatment of triples, CCSD(T). For our analysis we use accumulated data on relativistic effects on ionization potentials, electron affinities and polarizabilities of the coinage elements, Cu, Ag, and Au and related series like Ia and IIa group elements. Next we analyze electric properties of diatomic molecules as CuF, AgF, and AuF, and compare electric properties and bonding energies of these molecules with intermetalics CuAl, AgAl, AuAl. Electric dipole moments and dipole polarizabilities of the series of oxides including a heavy atom, GeO, SnO, and PbO in their 1Σ ground states are also analyzed. Particular attention is paid to the dissociation energy of PbO and its electron affinity. The bonding character of the MeL series of complexes (Me=Cu, Ag, Au; L=H2O, NH3, and H2S) is explained by stressing the importance of the charge transfer from the lone pair of the ligand to the metal element. Relativistic effects which affect the Me electron affinity and polarizability facilitate understanding the trends of Me interactions with different ligands. We also mention using of the optimized virtual orbital space (OVOS) as an instrument which allows to circumvent problems with proper contraction needed for a specific approximate relativistic Hamiltonian. OVOS allows to reduce the computer time of correlated relativistic calculation by an order of magnitude.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80164267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-03-06DOI: 10.1163/157404006778330825
G. Maroulis, C. Makris
We have calculated the bond-length dependence of the static dipole polarizability and hyperpolarizability of F2 relying on finite-field density functional calculations. At the internuclear separation of Re = 2.66816 a0 we obtain α/e2a02Eh−1 = 8.73 (B3LYP) and 8.60 (B3PW91), Δα/ e2a02Eh−1= 6.42 (B3LYP) and 6.32 (B3PW91), γ/ e4a04Eh−3 = 535 (B3LYP) and 503 (B3PW91) with a large, flexible [9s6p4d1f] basis set. For all three properties we observe that both B3LYPand B3PW91 yield values above the more accurate CCSD(T) results: CCSD(T) < B3PW91 < B3LYP. The discrepancy between DFT and conventional ab initio methods is more pronounced for the anisotropy of the (hyper)polarizability.
{"title":"Static Dipole Polarizability and Hyperpolarizability of F2 from Density Functional Theory Calculations. Similarities and Dissimilarities with Conventional ab initio Results","authors":"G. Maroulis, C. Makris","doi":"10.1163/157404006778330825","DOIUrl":"https://doi.org/10.1163/157404006778330825","url":null,"abstract":"We have calculated the bond-length dependence of the static dipole polarizability and hyperpolarizability of F2 relying on finite-field density functional calculations. At the internuclear separation of Re = 2.66816 a0 we obtain α/e2a02Eh−1 = 8.73 (B3LYP) and 8.60 (B3PW91), Δα/ e2a02Eh−1= 6.42 (B3LYP) and 6.32 (B3PW91), γ/ e4a04Eh−3 = 535 (B3LYP) and 503 (B3PW91) with a large, flexible [9s6p4d1f] basis set. For all three properties we observe that both B3LYPand B3PW91 yield values above the more accurate CCSD(T) results: CCSD(T) < B3PW91 < B3LYP. The discrepancy between DFT and conventional ab initio methods is more pronounced for the anisotropy of the (hyper)polarizability.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82076105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1163/157404005776611484
G. Rollmann, P. Entel
We present results of first-principles calculations of structural, magnetic, and electronic properties of small Fe clusters. It is shown that, while the lowest-energy isomers of Fe3 and Fe4 obtained in the framework of density functional theory within the generalized gradient approximation (GGA) are characterized by Jahn-Teller-like distortions away from the most regular shapes (which is in agreement with other works), these distortions are reduced when electron correlation effects are considered explicitly as within the GGA+U approach. At the same time, the magnetic moments of the clusters are enhanced with respect to the pure GGA case, resulting in maximal moments (in the sense of Hund's rules) of 4 μB per atom for the ground state structures of Fe3 and Fe4, and a total moment of 18 μB for Fe5. This already happens for moderate values of the Coulomb repulsion parameter U ∼ 2.0 eV and is explained by changes in the electronic structures of the clusters.
{"title":"Electron correlation effects in small iron clusters","authors":"G. Rollmann, P. Entel","doi":"10.1163/157404005776611484","DOIUrl":"https://doi.org/10.1163/157404005776611484","url":null,"abstract":"We present results of first-principles calculations of structural, magnetic, and electronic properties of small Fe clusters. It is shown that, while the lowest-energy isomers of Fe3 and Fe4 obtained in the framework of density functional theory within the generalized gradient approximation (GGA) are characterized by Jahn-Teller-like distortions away from the most regular shapes (which is in agreement with other works), these distortions are reduced when electron correlation effects are considered explicitly as within the GGA+U approach. At the same time, the magnetic moments of the clusters are enhanced with respect to the pure GGA case, resulting in maximal moments (in the sense of Hund's rules) of 4 μB per atom for the ground state structures of Fe3 and Fe4, and a total moment of 18 μB for Fe5. This already happens for moderate values of the Coulomb repulsion parameter U ∼ 2.0 eV and is explained by changes in the electronic structures of the clusters.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84713191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1163/157404005776611411
D. Anick
Ab initio studies are carried out for the water tetramer with a single H replaced by D, (H2O)3(HDO). The isomer with D in a free position, H7DfO4, has ZPE 0.17 kcal/mol higher than the isomer with D in an H-bond, H7DbO4. The same ZPE difference is found for HbD7O4 vs HfD7O4. The difference may be large enough for a preference for H rather than D in a free position to be experimentally measurable. Exploration of the components of ZPE shows that the stretch component alone favors H7DfO4, but this is more than compensated by the bend and torsion components.
{"title":"Positional Isotope Effect for the Water Tetramer","authors":"D. Anick","doi":"10.1163/157404005776611411","DOIUrl":"https://doi.org/10.1163/157404005776611411","url":null,"abstract":"Ab initio studies are carried out for the water tetramer with a single H replaced by D, (H2O)3(HDO). The isomer with D in a free position, H7DfO4, has ZPE 0.17 kcal/mol higher than the isomer with D in an H-bond, H7DbO4. The same ZPE difference is found for HbD7O4 vs HfD7O4. The difference may be large enough for a preference for H rather than D in a free position to be experimentally measurable. Exploration of the components of ZPE shows that the stretch component alone favors H7DfO4, but this is more than compensated by the bend and torsion components.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75201054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-12-01DOI: 10.1163/157404005776611402
G. Maroulis
{"title":"Dedicated to the memory of Prof. Dr. Jaroslav Koutecký (1922-2005)","authors":"G. Maroulis","doi":"10.1163/157404005776611402","DOIUrl":"https://doi.org/10.1163/157404005776611402","url":null,"abstract":"","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77683443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-01DOI: 10.1163/1574040054047568
V. Vaishnavi, A. Vandenberg, Guangzhi Zheng, R. G. Singh
The problem of semantic heterogeneity has gained ever increasing attention as the world's digital information systems become more closely interconnected. Among the various interoperability problems faced by information integration solutions, the semantic interoperability problem has been growing in importance, with increasingly sophisticated approaches being proposed for its resolution. This article reviews the essential characteristics of the semantic heterogeneity problem and its solution approaches in various domains, and proposes frameworks for evaluating the problem and selecting an appropriate solution approach.
{"title":"Semantic Heterogeneity: Problem and Solution Frameworks","authors":"V. Vaishnavi, A. Vandenberg, Guangzhi Zheng, R. G. Singh","doi":"10.1163/1574040054047568","DOIUrl":"https://doi.org/10.1163/1574040054047568","url":null,"abstract":"The problem of semantic heterogeneity has gained ever increasing attention as the world's digital information systems become more closely interconnected. Among the various interoperability problems faced by information integration solutions, the semantic interoperability problem has been growing in importance, with increasingly sophisticated approaches being proposed for its resolution. This article reviews the essential characteristics of the semantic heterogeneity problem and its solution approaches in various domains, and proposes frameworks for evaluating the problem and selecting an appropriate solution approach.","PeriodicalId":101169,"journal":{"name":"Soft Computing Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85226436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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