Essays on firm efficiency with imperfectly competitive input markets: an empirical analysis

In the thesis I exploit an empirical analysis on firm'’s productivity. I relate the efficiency at plant level with the input market features and I suggest an estimation technique for production function that takes into account firm'’s liquidity constraints. The main results are three. When I consider services as inputs for manufacturing firm’'s production process, I find that more competition in service sector affects positively plant’s productivity and export decision. Secondly liquidity constraints are important for the calculation of firm'’s productivity because they are a second source of firm's heterogeneity. Third liquidity constraints are important for firm'’s internationalization

Spectrum shaping and its application: spread-spectrum clock generator and circuits for ultra wide band

Electromagnetic spectrum can be identified as a resource for the designer, as well as for the manufacturer, from two complementary points of view: first, because it is a good in great demand by many different kind of applications; second, because despite its scarce availability, it may be advantageous to use more spectrum than necessary. This is the case of Spread-Spectrum Systems, those systems in which the transmitted signal is spread over a wide frequency band, much wider, in fact, than the minimum bandwidth required to transmit the information being sent. Part I of this dissertation deals with Spread-Spectrum Clock Generators (SSCG) aiming at reducing Electro Magnetic Interference (EMI) of clock signals in integrated circuits (IC) design. In particular, the modulation of the clock and the consequent spreading of its spectrum are obtained through a random modulating signal outputted by a chaotic map, i.e. a discrete-time dynamical system showing chaotic behavior. The advantages offered by this kind of modulation are highlighted. Three different prototypes of chaos-based SSCG are presented in all their aspects: design, simulation, and post-fabrication measurements. The third one, operating at a frequency equal to 3GHz, aims at being applied to Serial ATA, standard de facto for fast data transmission to and from Hard Disk Drives. The most extreme example of spread-spectrum signalling is the emerging ultra-wideband (UWB) technology, which proposes the use of large sections of the radio spectrum at low amplitudes to transmit high-bandwidth digital data. In part II of the dissertation, two UWB applications are presented, both dealing with the advantages as well as with the challenges of a wide-band system, namely: a chaos-based sequence generation method for reducing Multiple Access Interference (MAI) in Direct Sequence UWB Wireless-Sensor-Networks (WSNs), and design and simulations of a Low-Noise Amplifier (LNA) for impulse radio UWB. This latter topic was studied during a study-abroad period in collaboration with Delft University of Technology, Delft, Netherlands.

Microrganismi probiotici per le piante: una strategia di riduzione degli input nella coltura del pomodoro col metodo biologico

In the recent years, consumers became more aware and sensible in respect to environment and food safety matters. They are more and more interested in organic agriculture and markets and tend to prefer ‘organic’ products more than their traditional counterparts. To increase the quality and reduce the cost of production in organic and low-input agriculture, the 6FP-European “QLIF” project investigated the use of natural products such as bio-inoculants. They are mostly composed by arbuscular mycorrhizal fungi and other microorganisms, so-called “plant probiotic” microorganisms (PPM), because they help keeping an high yield, even under abiotic and biotic stressful conditions. Italian laws (DLgs 217, 2006) have recently included them as “special fertilizers”. This thesis focuses on the use of special fertilizers when growing tomatoes with organic methods in open field conditions, and the effects they induce on yield, quality and microbial rhizospheric communities. The primary objective was to achieve a better understanding of how plant-probiotic micro-flora management could buffer future reduction of external inputs, while keeping tomato fruit yield, quality and system sustainability. We studied microbial rhizospheric communities with statistical, molecular and histological methods. This work have demonstrated that long-lasting introduction of inoculum positively affected micorrhizal colonization and resistance against pathogens. Instead repeated introduction of compost negatively affected tomato quality, likely because it destabilized the ripening process, leading to over-ripening and increasing the amount of not-marketable product. Instead. After two years without any significant difference, the third year extreme combinations of inoculum and compost inputs (low inoculum with high amounts of compost, or vice versa) increased mycorrhizal colonization. As a result, in order to reduce production costs, we recommend using only inoculum rather than compost. Secondly, this thesis analyses how mycorrhizal colonization varies in respect to different tomato cultivars and experimental field locations. We found statistically significant differences between locations and between arbuscular colonization patterns per variety. To confirm these histological findings, we started a set of molecular experiments. The thesis discusses preliminary results and recommends their continuation and refinement to gather the complete results.

Assessment of Daily Life Mobility Levels using Wearable Inertial Sensors and Minimun Measured Input Models

Tracking activities during daily life and assessing movement parameters is essential for complementing the information gathered in confined environments such as clinical and physical activity laboratories for the assessment of mobility. Inertial measurement units (IMUs) are used as to monitor the motion of human movement for prolonged periods of time and without space limitations. The focus in this study was to provide a robust, low-cost and an unobtrusive solution for evaluating human motion using a single IMU. First part of the study focused on monitoring and classification of the daily life activities. A simple method that analyses the variations in signal was developed to distinguish two types of activity intervals: active and inactive. Neural classifier was used to classify active intervals; the angle with respect to gravity was used to classify inactive intervals. Second part of the study focused on extraction of gait parameters using a single inertial measurement unit (IMU) attached to the pelvis. Two complementary methods were proposed for gait parameters estimation. First method was a wavelet based method developed for the estimation of gait events. Second method was developed for estimating step and stride length during level walking using the estimations of the previous method. A special integration algorithm was extended to operate on each gait cycle using a specially designed Kalman filter. The developed methods were also applied on various scenarios. Activity monitoring method was used in a PRIN’07 project to assess the mobility levels of individuals living in a urban area. The same method was applied on volleyball players to analyze the fitness levels of them by monitoring their daily life activities. The methods proposed in these studies provided a simple, unobtrusive and low-cost solution for monitoring and assessing activities outside of controlled environments.

Wheat and low-input agriculture: agronomic, nutritional and nutraceutical implications

Recently, the increasing interest in organic food products and environmental friendly practices has emphasized the importance of selecting crop varieties suitable for the low-input systems. Additionally, in recent years the relationship between diet and human health has gained much attention among consumers, favoring the investigations on food nutraceutical properties. Among cereals, wheat plays an important role in human nutrition around the world and contributes to the daily intake of essential nutrients such as starch and protein. Moreover, whole grain contains several bioactive compounds that confer to wheat-derived products unique nutraceutical properties (dietary fibre, antioxidants). The present research provided interesting insights for the selection of wheat genotypes suitable for low-input systems and the development of specific breeding programs dedicated to organic farming. The investigation involved 5 old not dwarf genotypes (Andriolo, Frassineto, Gentil rosso, Inallettabile, Verna) and 1 modern dwarf variety (Palesio), grown under biodynamic management, over two consecutive growing seasons (2009/2010, 2010/2011). Results evidenced that under low-input farming some investigated old wheat genotypes (Frassineto, Inallettabile) were comparable to the modern cultivar in terms of whole agronomic performance. As regards the nutritional and nutraceutical properties, some old genotypes (Andriolo, Gentil rosso, Verna) emerged for their relevant content of several investigated phytochemicals (such as insoluble dietary fibre, polyphenols, flavonoids, in vitro antioxidant activity) and nutrients (protein, lipid, minerals). Despite of the low technological features, the six wheat varieties grown under low-input management may efficiently provide raw material for the preparation of traditionally processed bread with valuable sensory and nutritional properties. Results highlighted that old wheat varieties have peculiar phytochemical composition and may be a valuable source of nutraceutical compounds. Some of the genetic material involved in the present study may be used in breeding programs aimed at selecting varieties suitable for low-input farming and rich in health-promoting compounds.

An Input-Process-Output Approach to Interorganizational Teams: The Influence of Work Group Diversity, Trust and Shared Leadership on Communication Network and Team Outputs.

The market’s challenges bring firms to collaborate with other organizations in order to create Joint Ventures, Alliances and Consortia that are defined as “Interorganizational Networks” (IONs) (Provan, Fish and Sydow; 2007). Some of these IONs are managed through a shared partecipant governance (Provan and Kenis, 2008): a team composed by entrepreneurs and/or directors of each firm of an ION. The research is focused on these kind of management teams and it is based on an input-process-output model: some input variables (work group’s diversity, intra-team's friendship network density) have a direct influence on the process (team identification, shared leadership, interorganizational trust, team trust and intra-team's communication network density), which influence some team outputs, individual innovation behaviors and team effectiveness (team performance, work group satisfaction and ION affective commitment). Data was collected on a sample of 101 entrepreneurs grouped in 28 ION’s government teams and the research hypotheses are tested trough the path analysis and the multilevel models. As expected trust in team and shared leadership are positively and directly related to team effectiveness while team identification and interorganizational trust are indirectly related to the team outputs. The friendship network density among the team’s members has got positive effects on the trust in team and on the communication network density, and also, through the communication network density it improves the level of the teammates ION affective commitment. The shared leadership and its effects on the team effectiveness are fostered from higher level of team identification and weakened from higher level of work group diversity, specifically gender diversity. Finally, the communication network density and shared leadership at the individual level are related to the frequency of individual innovative behaviors. The dissertation’s results give a wider and more precise indication about the management of interfirm network through “shared” form of governance.

Laser driven proton acceleration and beam shaping

In the race to obtain protons with higher energies, using more compact systems at the same time, laser-driven plasma accelerators are becoming an interesting possibility. But for now, only beams with extremely broad energy spectra and high divergence have been produced. The driving line of this PhD thesis was the study and design of a compact system to extract a high quality beam out of the initial bunch of protons produced by the interaction of a laser pulse with a thin solid target, using experimentally reliable technologies in order to be able to test such a system as soon as possible. In this thesis, different transport lines are analyzed. The first is based on a high field pulsed solenoid, some collimators and, for perfect filtering and post-acceleration, a high field high frequency compact linear accelerator, originally designed to accelerate a 30 MeV beam extracted from a cyclotron. The second one is based on a quadruplet of permanent magnetic quadrupoles: thanks to its greater simplicity and reliability, it has great interest for experiments, but the effectiveness is lower than the one based on the solenoid; in fact, the final beam intensity drops by an order of magnitude. An additional sensible decrease in intensity is verified in the third case, where the energy selection is achieved using a chicane, because of its very low efficiency for off-axis protons. The proposed schemes have all been analyzed with 3D simulations and all the significant results are presented. Future experimental work based on the outcome of this thesis can be planned and is being discussed now.