Automatic 3D object model construction is important in applications ranging from manufacturing to entertainment industry, since CAD models of existing objects may be either unavailable or unusable. We describe a prototype system for automatically registering and integrating multiple views of objects using surface depth data to construct their geometric models. New techniques for handling key issues such as robust estimation of view transformations relating multiple views and seamless integration of registered data to form an unbroken surface have been proposed and implemented in our system. Our system has been tested on depth data that were obtained using digital interferometry techniques as well as a laser range scanner. Experimental results on real object surfaces demonstrate the good performance of our system.

The impact ionization properties in InP have been studied by using an ensemble Monte Carlo (EMC) method. In our EMC model, analytical model which contains three conduction bands and three valance bands is adopted to describe the band structure. The electron and hole impact ionization rate is fitted to the available measurement in the wide range of electric field by using Keldysh formula. The steady properties of InP are presented and analyzed. Particularly, the impact ionization behaviors in InP under submicron scale are discussed in detail. It is found that the impact ionization coefficient is not only a function of the applied electric filed but also behaves a size-dependent property when the size is down to submicron scale. We also find that, the size-dependent impact ionization effect which results from the dead space effect and the confined size, can help to prevent the carriers from impact ionization. Finally, the ratio of the electron impact ionization coefficient and the hole impact ionization coefficient is further studied. By taking the size-dependent impact ionization effect into consideration, this ratio is no longer holding as a constant but changing with the size of the devices under the specific electric field. As the size scaling down, the ratio will tend to deviate from one unit, which may contribute to a new look at the noise theory of APD devices.

The traditional geological view holds that overpressure resists mechanical compaction during sedimentary burial, keeping effective stress approximately constant and thereby passively preserving porosity and permeability in deep reservoirs. However, this assumption has relied predominantly on theoretical inference and struggles to explain a widespread geomechanical paradox: in many overpressured formations, the magnitude of permeability enhancement significantly outpaces the degree of porosity preservation. To decode this paradox, we conducted a fundamental proof-of-concept study utilizing high-pressure percolation coupled with in situ micro-CT and fractal analysis to dynamically simulate the effects of overpressure on porous sandstone under constant mean effective stress. The results reveal a counterintuitive phenomenon: while the global porosity remained fundamentally stable, the absolute permeability demonstrated a significant ~8% enhancement. Microstructural analysis indicates that this enhancement is driven by localized hydraulic wedging and the reactivation of sub-resolution throats acting as topological bridges. This active topological optimization physically and mathematically manifests as: (1) the massive reconnection of macroscopic isolated pores; (2) an enhanced space-filling capacity of the flow network, evidenced by an increased coordination number and 3D pore space fractal dimension (D_f); and (3) the structural straightening of fluid pathways, rigorously quantified by a reduction in flow tortuosity and tortuosity fractal dimension (D_T). These findings, derived from a single well-characterized sandstone sample, demonstrate that overpressure-driven permeability enhancement is a physically plausible mechanism in tight sandstones. This discovery offers a candidate physical explanation for the anomalously high permeability observed in certain deep overpressured reservoirs. However, the generalizability of these results to reservoirs with differing porosities, mineralogies, and diagenetic histories remains to be evaluated through multi-sample studies.

Accurate prediction of overpressure in deep reservoirs is critical for hydrocarbon ex-ploration and development. Conventional approaches, such as interpolation of sin-gle-well pressure data and seismic inversion, often produce considerable errors and uncertainty when predicting overpressure in undrilled or inter-well areas, potentially leading to misinterpretation of reservoir pressure-field distributions. To address these limitations, this study proposes a novel approach that integrates identification of overpressure origins with quantitative analysis of the geological factors controlling overpressure magnitude. Multiple regression analysis enabled accurate prediction of overpressure in undrilled areas, with relative errors of less than 5% compared with measured pressures. Based on the conventional classification of normal and overpressure systems in the Bozhong area, three pressure-system types were identified: (1) paleo-overpressure converted to present-day normal pressure, (2) paleo-normal pressure retained as present-day normal pressure, and (3) paleo-overpressure preserved as present-day overpressure. The first type, character-ized by present-day pressure coefficients of 1.0–1.1, occurs predominantly near first- and second-order faults and is attributed to vertical fault opening and subsequent pressure release. The second type occurs mainly on structural slope highs and is asso-ciated with slow sedimentation rates and the absence of high-quality source rocks. The third type, with pressure coefficients ranging from 1.2 to 2.0, is primarily distributed in slope lows and depressions. It exhibits complex origins involving individual mecha-nisms, including undercompaction, hydrocarbon generation, pressure transfer, and tectonic compression, as well as coupled mechanisms, particularly undercompaction combined with hydrocarbon generation. This complex pressure system is controlled by several geological factors, including burial depth, sedimentation rate, vitrinite reflec-tance (Ro), total organic carbon content, fault throw, fault dip angle, and distance from faults.