Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis

Key management in wireless sensor networks faces several new challenges. The scale, resource limitations, and new threats such as node capture necessitate the use of an on-line key generation by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The practical advantage of this approach is that we do not require node movement. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the error correction property of the protocol mitigates the effects of measurement errors and other temporal effects, giving rise to an agreement rate of over 97%. We show the applicability of our protocol by implementing it on MICAz motes, and evaluate its robustness and secrecy through experiments and analysis.Comment: Submitted to IEEE Transactions on Dependable and Secure Computin

Information technology investments and impact on the productivity of firms : an empirical analysis in light of the productivity paradox

Este trabalho objetivou testar a ocorrência do Paradoxo da Produtividade em uma amostra de empresas brasileiras; este Paradoxo estabelece que os acréscimos nos investimentos em tecnologia da informação não são acompanhados por acréscimos na produtividade das empresas. A partir de uma amostra de 429 observações de 98 empresas brasileiras que, no período de 2000 a 2006, faturaram cerca de US$856 bilhões e operaram investimentos em tecnologia da informação de US$ 12,9 bilhões, foi testado um modelo baseado na função de produção de Cobb-Douglas, que apresentou indícios de que o acréscimo neste tipo de investimento foi acompanhado de um acréscimo positivo nas receitas. O trabalho mostrou, ainda, indícios de que houve eficiência marginal nos investimentos em tecnologia da informação e de que a relação entre as receitas e o número de funcionários empregados em TI alcançou um aparente ponto de saturação. Na análise dos resultados foram identificados comportamentos distintos entre os setores analisados e nas conclusões foram apresentados exemplos de como os resultados poderiam ser aplicados no suporte ao processo decisório do planejamento de investimentos e de estratégias de negócios em tecnologia da informação. Este trabalho objetivou testar a ocorrência do Paradoxo da Produtividade em uma amostra de empresas brasileiras; este Paradoxo estabelece que os acréscimos nos investimentos em tecnologia da informação não são acompanhados por acréscimos na produtividade das empresas. A partir de uma amostra de 429 observações de 98 empresas brasileiras que, no período de 2000 a 2006, faturaram cerca de US$856 bilhões e operaram investimentos em tecnologia da informação de US$ 12,9 bilhões, foi testado um modelo baseado na função de produção de Cobb-Douglas, que apresentou indícios de que o acréscimo neste tipo de investimento foi acompanhado de um acréscimo positivo nas receitas. O trabalho mostrou, ainda, indícios de que houve eficiência marginal nos investimentos em tecnologia da informação e de que a relação entre as receitas e o número de funcionários empregados em TI alcançou um aparente ponto de saturação. Na análise dos resultados foram identificados comportamentos distintos entre os setores analisados e nas conclusões foram apresentados exemplos de como os resultados poderiam ser aplicados no suporte ao processo decisório do planejamento de investimentos e de estratégias de negócios em tecnologia da informação. _________________________________________________________________________________ ABSTRACTThis study aimed to investigate the occurrence of the Productivity Paradox of information technology investments in a sample of Brazilian firms. This Paradox establishes that the increase in information technology investments is not accompanied by the increase of firms' productivity. The estimated model was based on the Cobb-Douglas production function and considered a sample of 429 observations of 98 Brazilian firms that had aggregated sales of over US$856 billion and had operated information technology investments around of US$ 12.9 billion during the period of 2000 to 2006. The estimated model showed evidence that changes in the information technology investments were statistically correlated with changes in productivity gains. In addition, the model showed that there was marginal efficiency in the information technology investments and that the functional relationship between production and the number of employees in information technology reached an apparent saturation point. The empirical results showed different behaviors among analyzed sectors and the findings were presented with examples of how the results could be applied to support information technology investments and business strategy processes

Gestión municipal y calidad del servicio en la municipalidad distrital de Caleta de Carquín

El trabajo realizado presenta el tema de la gestión municipal, la misma que es importante hoy en día a nivel de los gobiernos locales y lo corresponde con la calidad del servicio, ya que se requiere mejorar en el contexto que se ha considerado como es la municipalidad distrital de Caleta de Carquín, para determinar la relación entre ambas variables. En la metodología de investigación, se consideró el diseño no experimental, transaccional correlacional. La población de estudio la conformaron 50 trabajadores del área administrativa de la Municipalidad y fueron quienes entregaron información a través de la respuesta a dos cuestionarios aplicados por el investigador. Se llegó a la conclusión que las variables y sus dimensiones se relacionan entre sí, estableciéndose que para que haya calidad en el servicio se tiene que mejorar la gestión a nivel de la municipalidad

Quadrupolar XMCD at the Fe K -edge in Fe phthalocyanine film on Au: Insight into the magnetic ground state

Under the terms of the Creative Commons Attribution license.-- et al.The observation of an anomalous quadrupolar signal in x-ray magnetic circular dichroism (XMCD) at the Fe K-edge of iron phthalocyanine (FePc) films is reported. All ground states previously suggested for FePc are incompatible with the experimental data. Based on ab initio molecular orbital multiplet calculations of the isolated FePc molecule, we propose a model for the magnetic ground state of the FePc film that explains the XMCD data and reproduces the observed values of the orbital moments in the perpendicular and planar directions.The financial support of the Spanish financial agency MINECO MAT2011-23791 and MAT2014-53921-R, Aragonese DGA-IMANA E34 (co-funded by Fondo Social Europeo), and European Union FEDER funds is acknowledged. The research at UCSD was supported by the Office of Basic Energy Science, US Department of Energy, BES-DMS, funded by the Department of Energy Office of Basic Energy Science, DMR, under Grant No. DE FG03 87ER-45332.Peer Reviewe

Comparison of turbulence measurements by a CSAT3B sonic anemometer and a high-resolution bistatic Doppler lidar

Accurate measurements of turbulence statistics in the atmosphere are important for eddy-covariance measurements, wind energy research, and the validation of atmospheric numerical models. Sonic anemometers are widely used for these applications. However, these instruments are prone to probe-induced flow distortion effects, and the magnitude of the resulting errors has been debated due to the lack of an absolute reference instrument under field conditions. Here, we present the results of an intercomparison experiment between a CSAT3B sonic anemometer and a highresolution bistatic Doppler lidar, which is inherently free of any flow distortion. This novel remote sensing instrument has otherwise very similar spatial and temporal sampling characteristics to the sonic anemometer and hence served as a reference for this comparison. The presented measurements were carried out over flat homogeneous terrain at a measurement height of 30 m. We provide a comparative statistical analysis of the resulting mean wind velocities, the standard deviations of the vertical wind speed and the friction velocity and investigate the reasons for the observed deviations based on the turbulence spectra and co-spectra. Our results show an agreement of the mean wind velocity measurements and the standard deviations of the vertical wind speed with a comparability of 0.082 and 0.020ms$^{-1}$, respectively. Biases for these two quantities were 0.003 and 0.012ms$^{-1}$, respectively. Slightly larger differences were observed for friction velocity. Analysis of the corresponding co-spectra showed that the CSAT3B underestimates this quantity systematically by about 3%on average as a result of co-spectral losses in the frequency range between 0.1 and 5 s$^{-1}$. We also found that an angle-of-attack-dependent transducer-shadowing correction does not improve the agreement between the CSAT3B and the Physikalisch-Technische Bundesanstalt (PTB) lidar effectively

SPENDING AND SAVING HABITS OF UNIVERSITY STUDENTS

The spending behavior of college students combined with their limited understanding of money management promotes habits that may lead to costly financial mistakes in the future. The quantitative survey was conducted to determine  the spending and saving habits of randomly selected students from the college of business. These students were enrolled in Accountancy, Business Administration, and Office Administration programs in which majority (55%) are females. Of the 90 respondents, 76% received an allowance from their parents, 16% from their sponsors and 6% have part-time jobs, 2% have personal investments  where they get their allowances. Included in the survey questionnaire were their expenditures  from monthly allowances which include the following: 1) food, 2) travel, 3) clothing/accessories, 4) electronics gadgets, 4) groceries, 5) beauty products and services, 6) school supplies, 7) cellphone load, 8)  books and magazines. Results show that the top five priorities where students from the college of business spent their monthly allowance were clothing/accessories (41.1%), school supplies (37.8%), books (36.7%), beauty products (32.2%), and beauty services (27.8%). Students spending habits were identified. Peer pressure and quality of the products were some contributing factors in the buying decision of the students.  The majority (82.2%) of the students saved money from their monthly allowance. This study emphasized the need for financial literacy awareness among the students particularly in the college of business so they will learn to practice the correct skill in money management

Molecular tilting and columnar stacking of Fe phthalocyanine thin films on Au(111)

Scanning tunneling microscopy and x-ray absorption spectroscopic results at the Fe K edge of Fe phthalocyanine (FePc) thin films grown on Au substrates, together with theoretical calculations, allow us to refine the structure of the film. In particular, we show that the columnar stacking of the FePc molecules is different from that found in bulk ¿ and ß phases. Moreover, the molecules do not lay parallel to the surface of the substrate. These structural findings are relevant to understand magnetism of FePc films.The financial support of the Spanish financial agency MINECO MAT2011-2379 and MAT2014-53921-R, Aragonese DGA-IMANA E34 (co-funded by European Social Fund), as well as European Union FEDER funds is acknowledged. The sample preparation and initial structural characterization were supported by the Office of Basic Energy Science, U.S. Department of Energy, BES-DMS funded by the Department of Energy’s Office of Basic Energy Science, DMR under Grant No. DE FG03 87ER-45332 and NSF DMR 0847552.Peer Reviewe