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Relative humidity (RH) or moisture content in the environment is an imperative factor that needs to be considered when it comes to the stability-related issues of inhaled dry powder formulations. Spray drying is one primary used technique for producing inhalable powders. However, it is a process that often leaves the powders amorphous and physically unstable. The existence of amorphous materials in pharmaceutical powders can affect the processing, storage, and delivery properties. If stored improperly, amorphous powders would absorb relatively large amounts of water from the surrounding, impacting significantly the long-term stability and performance of the powder formulations. In addition, RH could also impact aerosol deposition by affecting the electrostatic charge of particles, because electrostatic charge is one of the five mechanisms that governs aerosol deposition in the lung. In this thesis, we investigated the role of RH in pharmaceutical dry powder aerosols, with the following specific objectives: 1. To investigate the protective effect of hydrophobic excipients (amino acids and sodium stearate) against moisture-induced deterioration of the aerosolization performance in highly hygroscopic spray-dried powders. 2. To investigate the effects of storage humidity and hydrophobic excipients on electrostatic charge profiles of spray-dried powders for inhalation, using a novel Bipolar Charge Analyzer (BOLARTM, Dekati®, Finland).

Laser-induced filling and temperature cycling experiments were conducted in the sample BaFCl0.5Br0.5:Sm2+. Under laser irradiation, the decay curve of the hole area is composed of a fast component and a slow component. In the temperature cycling curve, there are a slow decrease of the hole area from 77 to 200 K and a rapid drop above 300 K. The decay of the hole area with time at 77 k and 313 K follow a logarithmic law. Analysis of these results shows that there are two kinds of traps which govern hole burning and filling processes in the sample. One is related to some impurities or defects. Another is related to Sm3+ ions. The distribution of the potential well of the latter, produced by substitutional disorder, can be described by a two-level-system model.

A new emission line from ZnSe film was observed at 10 K under high excitation. It is located at 2.774 eV, 8.6 meV below the P line. This new line grows rapidly, shifts to lower energy and gets broader with increasing excitation power. It can be interpreted as the result of inelastic scattering of a bound exciton with a free exciton. The relation between the emission intensity of this line and excitation intensity was deduced based on this model. The calculated curves fit the experimental data quite well.

An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to compose three Wheatstone bridges that are sensitive to the only given orientation. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, cross-axis-coupling degree, and linearity are presented. The sensitivity of X, Y and Z were 5.49 mV/g, 5.12 mV/g and 4.82 mV/g, respectively; the nonlinearity of X, Y and Z were 0.01%, 0.04% and 0.01%, respectively; the cross-axis-coupling factor of X axis to Y axis and Z axis are 0.119% and 2.26%; the cross-axis-coupling factor of Y axis to X axis and Z axis are 0.157% and 4.12%; the cross-axis-coupling factor of Z axis to X axis and Y axis are 0.511% and 0.938%. The measured performance indexes attain accurate vector-detection in practical applications, and even at a navigation level. In conclusion, the accelerometer is a highly integrated sensor.

A kind of piezoresistive ultrasonic sensor based on MEMS is proposed, which is composed of a membrane and two side beams. A simplified mathematical model has been established to analyze the mechanical properties of the sensor. On the basis of the theoretical analysis, the structural size and layout location of the piezoresistors are determined by simulation analysis. The boron-implanted piezoresistors located on membrane and side beams form a Wheatstone bridge to detect acoustic signal. The membrane-beam microstructure is fabricated integrally by MEMS manufacturing technology. Finally, this paper presents the experimental characterization of the ultrasonic sensor, validating the theoretical model used and the simulated model. The sensitivity reaches −116.2 dB (0 dB reference = 1 V/μbar, 31 kHz), resonant frequency is 39.6 kHz, direction angle is 55°.

The design, fabrication and packaging of a type of MEMS piezoresistive ultrasonic transducer array are introduced. The consistency of the resonance frequency and the sensitivity of the array are tested. Moreover, we detect the directivity and the multi-target identification ability of the array. The results of the consistency of the resonance frequency and the sensitivity show that there is a gap between the practical and theoretical results. This paper analyzes this problem in detail and points out the direction of improvement. As for the directivity, the actual result is consistent with the theoretical one. The results of multiple target distinguishing tests demonstrate that the smallest resolution angle of the array is 5.72° when the distance between the sensor array and measured objects is 2 m.

With the springing up of the MEMS industry, research on accelerometers is focused on miniaturization, integration, high reliability, and high resolution, and shares extensive application prospects in military and civil fields. Comparing with the traditional single cantilever beam structure or "cantilever-mass" structure, the proposed structure of "8-beams/mass" with its varistor completely symmetric distribution in micro-silicon piezoresistive triaxial accelerometer in this paper has a higher axial sensitivity and smaller cross-axis sensitivity. Adopting ANSYS, the process of structural analysis and the manufacturing flow of sensing unit are showed. In dynamic testing conditions, it can be concluded that the axial sensitivity of x, y, and z are Sx = 48 μV/g, Sy = 54 μV/g and Sz = 217 μV/g respectively, and the nonlinearities are 0.4%, 0.6% and 0.4%.

By measuring the excitation spectra of the 4f5d bands and the fluorescent decays of the 5D J 7F 0 (J =2,1,0) transition probability depending on temperature in M yM ′ 1-y F Cl x Br 1-x :Sm 2+ ( M =Mg, Ca, Sr, Ba)series, we have studied the dependence of the energy separation between the 4f5d bands and the 5D J level, the 5D J 7F 0(J=2,1,0 ) transition probability on the composition grade ( x ) and ( y ) and the effect on hole burning efficiency. We draw conclusions as below: In M yM ′ 1-y FCl x Br 1-x :Sm 2+ series, the 4f5d bands will be more close to the 5D J level with the increase of the Br concentration and the concentration of small radium alkaline earth ion, and this situation makes the 5D J 7F 0 electron transition probability increase. By reasoning, the hole burning efficiency of Sm 2+ are expected to be enhanced.

An analytical expression for the impact cross section of rare-earth centres in solids has been deduced. The impact cross sections of four different Er3+ centres in ZnS were calculated. The calculated data are in reasonable agreement with the experimental results. The impact cross sections of different excited states of Ho3+ centres in ZnS were also calculated.

The photoconductivity bands corresponding to the transitions from 6A1 to 4T1, 4T2 and 4E of Mn2+ in ZnSxSe1-x (x=0, 0.01, 0.02, 0.05, 0.10, 0.14) are found. The intensities of these bands relative to that of the intrinsic photoconductivity band are found to vary with x. The configuration model of the manganese centre in ZnSxSe1-x is proposed to explain the experimental results. The positions of the energy levels of Mn2+ in ZnSxSe1-x (x=0-0.10) relative to the conduction band are deduced systematically. The minimum of the configuration curve for 6A1 of Mn2+ is deduced to be 0.44 eV above that of the valence band of ZnSe. The threshold energy for optical excitation from the valence band to ZnSe to the 6A1 state of Mn2+ is found to be 0.69 eV.

ZnS thin films doped with Mn2+ ions or rare-earth ions are promising material for electroluminescent planar panels, which might be strong candidates for the next generation solid planar display devices to partly replace cathode-ray tube displays. They are attracting an increasing amount of research.