Papers by Silviu Cojocaru
Journal of Physics: Conference Series, 2010
ABSTRACT Lattice and charge degrees of freedom of cuprate superconductors remain an intensively d... more ABSTRACT Lattice and charge degrees of freedom of cuprate superconductors remain an intensively debated topic, both experimentally and theoretically, because of the strong anomalies observed in some of the phonon branches. In particular, the bond-stretching phonon modes show a knee like softening and a large damping for momenta around 0.25–0.3 r.l.u. along, e.g., (1, 0, 0) direction of the Brillouin zone. We discuss a phenomenological model where these anomalies are caused by coupling to electron charge fluctuations and explore a possibility to extract the spectrum of the latter from the phonon data. In particular, we predict a significant deviation from the standard value of the oxygen isotope substitution effect on the phonon spectrum itself. The phonon dispersion and linewidth are shown to contain complementary information related to the isotope effect which could allow a detailed description of the electronic spectrum.
ROMOPTO '97: Fifth Conference on Optics, 1998
Since the theoretical studies of Liu and Cohen who predicted the existence of a superhard phase o... more Since the theoretical studies of Liu and Cohen who predicted the existence of a superhard phase of carbon nitride, a great deal of effort was underdone in order to synthesize this hypothetical material with a nitrogen content as high as the 57% present in a (beta) -C3N4 structure. This study presents an attempt to produce CNx thin films using the
Applied Physics A Materials Science & Processing, 2001
. In this work, we present results of the synthesis and characterization of iron and iron oxide... more . In this work, we present results of the synthesis and characterization of iron and iron oxide nanoparticles aggregated in filamentary, spider-web-like structures. The particles were produced in a flow reactor by CO2 laser pyrolysis of gaseous mixtures of iron pentacarbonyl and ethylene. Low- and high-resolution electron microscopy reveals chain-like structures of particles, most of them being composed of an
Carbon, 1998
ABSTRACT We describe the possibility to synthesize carbon nitride fine powder by laser pyrolysis ... more ABSTRACT We describe the possibility to synthesize carbon nitride fine powder by laser pyrolysis of acetylene/nitrous oxide/ammonia mixtures. The powders were produced in a flow reactor by varying the relative concentrations of the sensitizers (). The kinetics of the reaction was monitored by IR spectrophotometry of the exhaust gases. The powder crystallinity and bond structure was studied by X-ray diffraction (XRD) and IR transmission spectrometry, respectively. The majority of XRD data suggests the presence of the predicted α- and β-C3N4 structures, with a concentration depending on starting conditions. The presence of CN bonded phases seems relevant. Under the present conditions, the slight contamination of powders by SF6 decomposition products could not be avoided.
Journal of Nanoparticle Research, 1999
Pulsed CO 2-laser-induced decomposition of different mixtures of SiH 4 and C 2 H 2 in a flow reac... more Pulsed CO 2-laser-induced decomposition of different mixtures of SiH 4 and C 2 H 2 in a flow reactor has been employed to produce silicon carbide clusters and nanoparticles with varying content of carbon. The as-synthesized species were extracted from the reaction zone by a conical nozzle and expanded into the source chamber of a cluster beam apparatus where, after having traversed a differential chamber, they were analyzed with a time-of-flight mass spectrometer. Thin films of silicon carbide nanoclusters were produced by depositing the clusters at low energy on potassium bromide and sapphire windows mounted into the differential chamber. At the same time, Si and SiC nanoparticles were collected in a filter placed into the exhaust line of the flow reactor. Both beam and powder samples were characterized by FTIR spectroscopy. The close resemblance of the spectra suggests that the composition of the beam and powder particles obtained during the same run is nearly identical. XRD spectroscopy could only be employed for the investigation of the powders. It was found that CO 2 laser pyrolysis is ideally suited to produce silicon carbide nanoparticles with a high degree of crystallinity. Nanopowders produced from the pyrolysis of a stoichiometric (2 : 1) mixture of SiH 4 /C 2 H 2 were found to contain particles or domains of pure silicon. The characteristic silicon features in the FTIR and XRD spectra, however, disappeared when C 2 H 2 was applied in excess.
Materials Chemistry and Physics, 1998
The synthesis of nanosized (l-100 nm) particles is an active research field in chemical processin... more The synthesis of nanosized (l-100 nm) particles is an active research field in chemical processing technologies. The process may be of particular relevance in the case of the widely used iron-based materials. In this paper, we report on the preparation and characterization of ultrafine powders produced by pulsed infrared laser pyrolysis of iron pentacarbonyl, Fe(CO),, in sensitized mixtures. The synthesis is performed in a flow reactor, at rather high pressure (400 mbar) and high laser fluence (-5 J cm-'). The average diameter of the particles is 30 nm. Different characterization methods of the fine powder aged in atmosphere indicate the presence of a substantial oxidic portion, identified as the P-F%03. HZ0 form. Some experimental observations suggest the possibility of iron-oxides formation during synthesis in the flow reactor. The relevant mechanisms for this reaction route are discussed.
Le Journal de Physique IV, 1999
lron carbides and iron conlposites present a particular interest due to their nlagnetic and catal... more lron carbides and iron conlposites present a particular interest due to their nlagnetic and catalytic properties which could be highly enhanced if particles in the ~~la~onletric size range were used. We present results on the synthesis and characterization of iron-carbide na~~oparticles by sensitized C02 laser pyrolysis of gas ~~~i s t u r e s containing iron pentacarbor~yl (vapors) and eti~yIene/acetylene precursors. The influence of the natnre of hydrocarbon on the stn~ctural properties of tl~e nanopwders are revealed by mfferenl analylical techniqnes (JR spectrophotometry, X-ray dffraction, transn~ission electron microscopy and Mossbauer spectroscopy).
Applied Physics A: Materials Science & Processing, 1997
3 N4 structure, with an α-C3N4-like form being prevalent. The powders were found to be slightly ... more 3 N4 structure, with an α-C3N4-like form being prevalent. The powders were found to be slightly contaminated by SF6 sensitizer products. Our results suggest that by improving the experimental parameters this contamination might be reduced and that the laser pyrolysis method offers possibilities for production of CxNy materials, with controlled composition.
Le Journal de Physique IV, 1999
Manager Journal, 2015
The medical field is one of the most dynamic in Romania, regarding the adoption of IT. Dynamics i... more The medical field is one of the most dynamic in Romania, regarding the adoption of IT. Dynamics is determined by two main factors. The first is related to the development of private health care market, and the second the benefits of using new technologies in medical processes. Telemedicine and advanced medical techniques are driven by new technologies. This paper aims to analyse the use of technology interoperability standards between applications and devices in medical institutions from Romania. Adoption of standards such as HL7 (Health Level 7), XML (eXtended Markup Language) and SOA (Service Oriented Architecture) can increase the quality of medical processes in Romania and can help reduce the cost of medical processes. In the article present a brief study on the use of new technologies in SMURD (Mobile Emergency Service for Resuscitation and Extrication). SMURD implementation is a clear proof of how technology could bring leadership in medical care
In tlhs paper we consider same series attached to the Smarandache function.
Manager Journal, 2012
Despite the limits imposed by the computer’s impossibility to perfectly duplicate the human reaso... more Despite the limits imposed by the computer’s impossibility to perfectly duplicate the human reasoning, the information systems that assist decision making and the business intelligence components are considered nowadays compulsory instruments of the modern manager; most of the daily decision procedures, the information required by the decision making process together with the information search and retrieval techniques are taken over completely by these systems. Furthermore, their continuous development, doubled the improvement of computers’ performances, offer increased possibilities to take over major parts of some of the most intense reasoning activities performed by humans.
Manager Journal, 2013
IT&C companies need to adapt themselves to an environment featuring a high level of competition. ... more IT&C companies need to adapt themselves to an environment featuring a high level of competition. Innovation stays as the main vector of the domain, while the renewal rate of new technologies grows in speed (there are cases where new technologies emerge and replace the older ones in months). With this series of research we aim to analyse several local or global companies within the IT&C field, as well as the importance of leadership for their development. This first article will focus on leadership within a company called Research In Motion – RIM (currently named BlackBerry) and on the main problems that have arisen within the company after the organisation was left without support from the leaders that created its worldwide brand.
Manager Journal, 2013
The concept of leadership is extremely complex and very often, there is a confusion between leade... more The concept of leadership is extremely complex and very often, there is a confusion between leadership and management. Although people are using these words interchangeably, they play very different, but still essential, roles. This paper aims to present a case study regarding an implementation project in banking back-office activities, in order to prove the importance of managing correct the back-office resources, but in the same time the need for a vision that would lead the people toward the scope of a project. The paper describes the existence of a relationship between leadership and operational excellence, also.
Web Services and Service Oriented Architecture (SOA) registered an important increase in the past... more Web Services and Service Oriented Architecture (SOA) registered an important increase in the past years. The aim of the Paper is to analyse the manner in which these technologies are used by the local business and how they can lead to the improvement of processes within enterprises. The paper includes the results of a study dedicated to determine the level of usage of these technologies in Romanian companies.
The mobile device market proved one of the most dynamic, with the leader in intelligent phones ch... more The mobile device market proved one of the most dynamic, with the leader in intelligent phones changing at least four times during the last decade. At least one important acquisition was registered during 2013 (when Microsoft bought Nokia’s mobile phone division) and this event is slated to induce major shifts within the structure of this market. With this story we aim to provide information related to trends foreseen for this market.
In 1979, Sony launched a portable Walkman range. For nearly a quarter of century, the Sony Walkma... more In 1979, Sony launched a portable Walkman range. For nearly a quarter of century, the Sony Walkman was the undisputed market leader and Sony was considered a top innovative company. Then, in 2001, Apple decided to launch the iPod, a new portable player. About 80% of the iPod technical components (e.g. memory, storage media) were produced by various companies within the Sony group. In 2004, iPod sales overtake Sony Walkman globally and become the new market leader in portable players. How was this possible? Theoretically, Sony held all conditions for launching the new generation of portable players, but instead, a new company – Apple – completely changed the market.
Established in 1911, IBM is an example of leadership in technology. IBM has been linked since the... more Established in 1911, IBM is an example of leadership in technology. IBM has been linked since the beginning of computing, being the company that invented the tabs (forerunner of the current computer). In 2012, IBM ranked No. 2 in the U.S. in terms of number of employees (435,000 worldwide, 100,000 in the United States). IT vertical market is characterized by a very important contribution to innovation and, therefore, the rankings are very dynamic field. IBM was able to create a value system in the organization and also a leadership system, thus managing to retain its leading position in the market.
The Single Euro Payments Area is a payment-integration project of the European Union.SEPA is aimi... more The Single Euro Payments Area is a payment-integration project of the European Union.SEPA is aiming to create an integrated euro payments market and to harmonize the national and crossborder euro payment systems, making cross-border transactions as simple and cheap as national ones. The SEPA regulations is aiming to increase harmonization, through using of common payments formats and computer languages. The goal of using a common standard in the industry in order to facilitate interoperability among systems and infrastructures, will be more and more important. In this view, standardizing messages across institutions and companies has never been more important. The ISO 20022 provides interoperability and consistency to a highly complex industry, thereby reducing the risk of errors and speeding up processes
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Papers by Silviu Cojocaru