Ultrasonic techniques were used to detect hollow heart in potatoes nondestructively. Fifty Russet Burbank potatoes were evaluated physically and sonically. A pair of dry-coupling 50-kHz ultrasonic transducers were used to generate an ultrasonic pulse with a power level of 0.22 W for the test of acoustic transmission through whole potato tuber in a transverse direction at different locations along the longitudinal axis with a certain interval distance. It was found that the waveform analyses in time domain for a series of transmitted signals along the longitudinal axis of potato tuber, yielded the potential in detecting hollow heart in potatoes noninvasively. The transmission losses for potatoes having hollow heart were found to be greater than 0.28 dB/mm. This value was used as a criterion to indicate potatoes with hollow heart at an accuracy of 98 percent. The ability to detect hollow heart in potatoes was limited to a minimum cavity size of 0.5 cm3 because the interval distance between locations of measurement was relatively large compared to the size of the projected area of hollow heart. The accuracy of the detection would be improved if a smaller contact area for the transmitting transducer were used, and if the intervals between ultrasonic measurement locations were smaller. Physical properties of the tested potatoes were also recorded for consideration of their relationships with ultrasonic parameters. Physical properties of tested potatoes such as modulus of elasticity, tuber length, diameter, and weight, were found to have poor correlation with ultrasonic parameters such as ultrasonic velocity, attenuation coefficient, and root mean square voltage of transmitted signal. This study showed that if all potatoes with weights of 300 g or less were eliminated from a mass of incoming potatoes, only 80 percent of the total mass would have to be examined for hollow heart. / Master of Science

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第12762号 / 論農博第2785号 / 新制||農||1016(附属図書館) / 学位論文||H25||N4785(農学部図書室) / 30614 / (主査)教授 奥村 正悟, 教授 中野 隆人, 教授 吉村 剛 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Ce mémoire de thèse étudie diverses méthodes d'amélioration des interféromètres atomiques. Dans la première partie du manuscrit, nous analysons comment une détection non-destructive, au sens où elle préserve la cohérence entre les états internes de l'ensemble atomique, permet d'améliorer la sensibilité des interféromètres. Nous montrons tout d'abord, grâce à une étude théorique, que la projection du vecteur d'onde engendrée par la mesure permet de préparer des états comprimés de spin. Nous présentons ensuite la mise en œuvre de cette méthode à l'aide d'une détection reposant sur la spectroscopie par modulation de fréquence. Finalement, nous exposons quelques premières applications de cette détection non-destructive, plus précisément nous présentons la réalisation du rétroaction quantique qui protège l'état atomique contre la décohérence induite par un basculement du spin collectif, nous montrons aussi comment réaliser une boucle à verrouillage de phase où les atomes servent de référence de phase. Dans la seconde partie du manuscrit, nous présentons la réalisation tout-optique d'un condensat de Bose-Einstein dans une cavité de haute finesse, exploitant les technologies développées pour les télécommunications optiques. Nous commençons par une analyse du résonateur et des méthodes d'asservissement, nous introduisons notamment une méthode d'asservissement originale exploitant la modulation serrodyne. Enfin, nous montrons comment un condensat est obtenu par évaporation dans le mode optique de la cavité. / In this thesis, we study several methods to improve atom interferometers. In the first part of the manuscript, we analyze how a nondestructive detection, that preserves the coherence between the internal degrees of freedom in an atomic ensemble, can be used to increase the sensitivity of interferometers. We first theoretically show how the projection of the wave-function induced by the measurement prepares spin-squeezed states. We then present the implementation of this method with a detection based on the frequency modulation spectroscopy. Finally, some first applications are described, more explicitly we show how to implement a quantum feedback that preserve the atomic state against the decoherence induced by a random collective flip, we also introduce a phase-locked loop where the atomic sample is used as the phase reference. In the second part of the manuscript, we present the all-optical realization of a Bose-Einstein condensate in a high-finesse cavity using a laser system based on standard telecoms technologies. We first describe the resonator and the frequency lock of the laser on the resonance, in particular, we introduce a new stabilization method based of the serrodyne modulation. Finally, we show how the condensate is obtained from the evaporation in the cavity mode.