Performance Enhancement of Logistic Regression for Big Data on Spark

This research proposes a new ftting algorithm of logistic regression on IRWLS that utilizes the procedure of scanning data row-by-row and has the ability to acquire an exact result with only a few iterations. Furthermore, this research also realizes the distributed parallelization of the proposed method on Spark and conducts various experiments to manifest its memory-wise advantage over the traditional methods such as Spark MLlib package. The results show that the proposed method can provide an exact result rather than an approximated one within 5 or 6 iterations; achieve a satisfying accuracy for fight delay prediction within 1 or 2 iterations; has a better potential for parallelization and a better performance than MLlib with a 3-4x faster speed without full optimizations; and its performance is not undermined by an increasing data memory ratio

A Comparative Study Based on Provincial Performance

This thesis attempts to transfer the spotlight upon the political issue about democratization in China to something else that has not been spared enough attention yet. Here it refers to the transformation of governance mode. The rather rapid industrialization and urbanization in the process of modernization in China does not aggravate the swelling of bureaucratic system to the extent that largely increases financial burden, internal disorder, and inefficiency. The maintenance of a stable and controllable government on both national and local level benefits from the transformation of governance mode from command mode to network mode

Urban Conservation in China: The reasons and conflicts of historical neighborhood preservation

Historical neighborhood conservation plays an important part in the inner city redevelopment in China. The purpose of this thesis is to identify and understand the complexity of stakeholders' incentives and their responsibilities in historical neighborhood conservation in Chinese urban contexts by analysis two cases in Beijing and Shanghai. The two research questions are: 1) who are the stakeholders and what are their incentives in an urban conservation project? 2) What social, political, and economic factors affect decisions to preserve neighborhoods in Chinese cities? From the analysis, political implications are drawn that: 1) The governments should encourage and solicit original residents participation on a historical neighborhood conservation project. 2) The governments should introduce the private capital into the neighborhood conservation project

Sensitivity of intracavity filtering schemes for detecting gravitational waves

We consider enhancing the sensitivity of future gravitational-wave detectors by adding optical filters inside the signal-recycling cavity -- an intracavity filtering scheme, which coherently feeds the sideband signal back to the interferometer with a proper frequency-dependent phase. We study three cases of such a scheme with different motivations: (i) the case of backaction noise evasion, trying to cancel radiation-pressure noise with only one filter cavity for a signal-recycled interferometer; (ii) the speed-meter case, similar to the speed-meter scheme proposed by Purdue and Chen [Phys. Rev. D 66, 122004 (2002)] but without the resonant-sideband-extraction mirror, and also relieves the optical requirement on the sloshing mirror; (iii) the broadband detection case with squeezed-light input, numerically optimized for a broadband sensitivity.Comment: 10 pages, 10 figure

Numerical Modeling of Debris Flows Induced by Dam-Break Using the Smoothed Particle Hydrodynamics (SPH) Method

Dam-break flows may change into debris flows if certain conditions are satisfied, such as abundant loose material and steep slope. These debris flows are typically characterized by high density and can generate strong impact forces. Due to the complexity of the materials that they are made of, it has always been very challenging to numerically simulate these phenomena and accurately reproduce experimentally debris flows’ processes. Therefore, to fill this gap, the formation-movement processes of debris flows induced by dam-break were simulated numerically, modifying the existing smoothed particle hydrodynamics (SPH) method. By comparing the shape and the velocity of dam break debris flows under different configurations, it was found that when simulating the initiation process, the number of particles in the upstream section is overestimated while the number of particles in the downstream area is underestimated. Furthermore, the formation process of dam-break debris flow was simulated by three models which consider different combinations of the viscous force, the drag force and the virtual mass force. The method taking into account all these three kinds of interface forces produced the most accurate outcome for the numerical simulation of the formation process of dam-break debris flow. Finally, it was found that under different interface force models, the particle velocity distribution did not change significantly. However, the direction of the particle force changed, which is due to the fact that the SPH model considers generalized virtual mass forces, better replicating real case scenarios. The modalities of dam failures have significant impacts on the formation and development of debris flows. Therefore, the results of this study will help authorities to select safe sites for future rehabilitation and relocation projects and can also be used as an important basis for debris flow risk management. Future research will be necessary to understand more complex scenarios to investigate mechanisms of domino dam-failures and their effects on debris flows propagation

Numerical Simulation of Non-Homogeneous Viscous Debris-Flows Based on the Smoothed Particle Hydrodynamics (SPH) Method

Non-homogeneous viscous debris flows are characterized by high density, impact force and destructiveness, and the complexity of the materials they are made of. This has always made these flows challenging to simulate numerically, and to reproduce experimentally debris flow processes. In this study, the formation-movement process of non-homogeneous debris flow under three different soil configurations was simulated numerically by modifying the formulation of collision, friction, and yield stresses for the existing Smoothed Particle Hydrodynamics (SPH) method. The results obtained by applying this modification to the SPH model clearly demonstrated that the configuration where fine and coarse particles are fully mixed, with no specific layering, produces more fluctuations and instability of the debris flow. The kinetic and potential energies of the fluctuating particles calculated for each scenario have been shown to be affected by the water content by focusing on small local areas. Therefore, this study provides a better understanding and new insights regarding intermittent debris flows, and explains the impact of the water content on their formation and movement processes

How Story Works in Mobile App Stores? Exploring the Same-Side Effect from the Storytelling Perspective

The growing number of mobile apps has contributed to an innovation diffusion paradox whereby the accelerated pace with which mobile apps are being developed and updated has stymied their own diffusion. Due to consumers’ limited personal involvement with mobile apps, storytelling, as an emerging and novel product recommendation format, is gaining traction as a promotional mechanism for diffusing mobile apps within the ecosystem. Storytelling is particularly amenable to the context of mobile app stores by giving affective meaning to the focal app being promoted and strengthening its association with other apps available from these stores. To this end, we construct a research model to illustrate how consumers’ demand for related mobile apps is shaped by similarity in functional and visual attributes between these apps and the focal app being promoted via storytelling. Our model also sheds light on how the preceding effects could be mitigated by within-developer influence