The dynamic process of economic takeoff and industrial transformation

This paper studies the patterns and key determinants of staged economic development. We construct a two-sector dynamic general equilibrium model populated with one-period lived non-overlapping generations, featuring endogenous enhancement in modern technology and endogenous accumulation of labor skills and capital funds. We consider preference biases toward the traditional sector of necessities, capital barriers to the modern sector, and imperfect substitution between skilled and unskilled workers. By calibrating the model to �t historic U.S. development, we fi�nd that modern technologies, saving incentives and capital fundings are most important determinants of the takeoff time. By evaluating the process of economic development, we identify that saving incentives is most crucial for the speed of modernization. We also study how labor and capital allocations toward the modern industry respond to various preference, technology and institutional changes. We further establish that labor, capital and output are most responsive to the initial state of modern technologies but least responsive to the initial state of skills, along the dynamic transition path.Economic takeoff and industrial transformation; endogenous skill and technological advancements; saving incentives, preference biases and capital barriers

Energetics of collapsible channel flow with a nonlinear fluid-beam model

We consider flow along a finite-length collapsible channel driven by a fixed upstream flux, where a section of one wall of a planar rigid channel is replaced by a plane-strain elastic beam subject to uniform external pressure. A modified constitutive law is used to ensure that the elastic beam is energetically conservative. We apply the finite element method to solve the fully nonlinear steady and unsteady systems. In line with previous studies, we show that the system always has at least one static solution and that there is a narrow region of the parameter space where the system simultaneously exhibits two stable static configurations: an (inflated) upper branch and a (collapsed) lower branch, connected by a pair of limit point bifurcations to an unstable intermediate branch. Both upper and lower static configurations can each become unstable to self-excited oscillations, initiating either side of the region with multiple static states. As the Reynolds number increases along the upper branch the oscillatory limit cycle persists into the region with multiple steady states, where interaction with the intermediate static branch suggests a nearby homoclinic orbit. These oscillations approach zero amplitude at the upper branch limit point, resulting in a stable tongue between the upper and lower branch oscillations. Furthermore, this new formulation allows us to calculate a detailed energy budget over a period of oscillation, where we show that both upper and lower branch instabilities require an increase in the work done by the upstream pressure to overcome the increased dissipation.Comment: 27 pages, 10 figures, under revie

Time-based low dropout regulator

The low dropout regulator (LDO) is an essential building block for modern integrated circuits. Traditional analog design faces formidable challenges as technology scales down, such as lower supply voltage and channel length modulation. Digital LDOs do not have the problems that analog LDOs have, but they usually have worse performance metrics. Therefore, a time-based LDO is proposed to combine the merits of both analog and digital together. In the end, the LDO achieves 0.6-1 V supply voltage range and 0.5-0.9 V output voltage range. The maximum output current is 50 mA and the worst case transient time is 1.58 μs under 0.6 V supply voltage. The maximum current efficiency is 99.98%

The energetics of self-excited oscillations in collapsible channel flows

In this thesis, we study the energetics of two-dimensional flow through a flexible-walled channel, where we mainly consider two models.The first model we consider is a fluid-membrane model in a long domain where the upper wall is replaced by elastic membrane under external pressure. The normal viscous stress, wall damping, wall inertia and membrane tension are all included in the membrane equation. We establish the corresponding eigenvalue problem of this model and trace the neutrally stable curves of this system across the parameter space. In agreement with previous work, we identify three different modes of instability (i:e: Tollmien-Schlichting waves (TS), traveling-wave flutter (TWF) and static divergence (SD) waves). We classify these instabilities into two classes (i:e: class A and class B form Benjamin [3]) using wall damping. Class A waves are destabilised by wall damping while class B waves are stabilised by wall damping. Furthermore, we consider the energy budget of the fully nonlinear system as well as that of the linearised system in order to determine whether the energy budget can be used to distinguish these different classes of instability. We found that the concept of ‘activation energy’ that connects with instability mode classification (Landahl [45], Cairns [17]) is not easily identified with terms in our energy budget. In particular, this wave energy is not equal to the work done by the fluid on the wall in our energy budget, as has previously been attributed to TWF. The second model we consider is a finite length fluid-beam model formed from a two dimensional channel, where one segment of the upper wall is replaced by a plane strained elastic beam subject to an external pressure. A parabolic inlet flow with constant flux is driven through the channel. We apply the finite element method with adaptive meshing to solve the fully nonlinear system numerically. We demonstrate the stability of the system after small stimulation, where the system exhibit large amplitude self-excited oscillations. In addition, large amplitude vorticity waves are found in the downstream segment of the flexible wall. The energy budget of this fully nonlinear system is calculated; the energy budget of the system balances the kinetic energy, the rate of working of external pressure and the dissipation energy over one oscillation. Moreover, we form the corresponding eigenvalue problem of the fluid-beam model by linearising the system about the corresponding static state to second order. A finite element method (similar to that of the fully nonlinear system) is employed to solve for the linear eigenfunctions. The observation of stability calculated from the eigenvalue problem are consistent with that calculatedfrom the fully nonlinear problem. We identify the stability of the system and establishthe neutral stability curve in the parameter space spanned by the beam extensional stiffness and Reynolds number. Two modes of instabilities are identified (i:e: mode-2 and mode-3, here the system is mode-i when the oscillation to the elastic beam contains i-half wavelengths). Finally, we derive the energy budget of the linearised system at second order. The energy budget of the linearised system exhibits a balance between the averaged second order dissipation energy, the work done by non-linear Reynolds stresses and the rate of working of perturbation fluid stress on the elastic wall. We anticipate that the precise balance of energy might serve as a robust method to distinguish the different modes of oscillation, although this has yet to be confirmed

Least squares estimation of spatial autoregressive models for large-scale social networks

Due to the rapid development of various social networks, the spatial autoregressive (SAR) model is becoming an important tool in social network analysis. However, major bottlenecks remain in analyzing largescale networks (e.g., Facebook has over 700 million active users), including computational scalability, estimation consistency, and proper network sampling. To address these challenges, we propose a novel least squares estimator (LSE) for analyzing large sparse networks based on the SAR model. Computationally, the LSE is linear in the network size, making it scalable to analysis of huge networks. In theory, the LSE is root n-consistent and asymptotically normal under certain regularity conditions. A new LSE-based network sampling technique is further developed, which can automatically adjust autocorrelation between sampled and unsampled units and hence guarantee valid statistical inferences. Moreover, we generalize the LSE approach for the classical SAR model to more complex networks associated with multiple sources of social interaction effect. Numerical results for simulated and real data are presented to illustrate performance of the LSE.National Natural Science Foundation of China [71532001, 11525101, 71332006, 11701560, 11401482]; Beijing Municipal Social Science Foundation [17GLC051]; Center for Applied Statistics, School of Statistics, Renmin University of China; Center of Statistical Research, Southwestern University of Finance and Economics; China's National Key Research Special Program [2016YFC0207700]; NSF [DMS-1309507, DMS-1418172]; NSFC [11571009]Open Access JournalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The Development Strategy of Shenyang Home Inns

Since its first budget hotel was located in Shenyang, Home Inns has opened numerous budget hotels every where. Such a fast development also brings out many problems and risks. As a leader of the budget hotel industry, Home Inns in Shenyang also has many problems to be sorted out urgently. We therefore analyzed the development and existing problems of Home Inns and provide relevant strategies for a consistent and healthily development of Home Inns. Key words: Home Inns; Development; Budget hote

Housing Dynamics: Theory Behind Empirics

We construct a dynamic general equilibrium model of housing, incorporating some key features that bridge time and space. We model explicitly the evolution of housing structures/household durables and the separate role played by land, fully accounting for households’ locational choice decisions. Housing services derive positive utility, but are decayed away from the city center. Our model enables a full characterization of the dynamic paths of housing as well as housing and land prices. The model is particularly designed to be calibrated to fit some important stylized facts, including faster growth of housing structure/household durables than housing, faster growth of land prices than housing prices, a locationally steeper land rent gradient than the housing price gradient, and relatively flatter housing quantity and price gradients in larger cities with flatter population gradients. The calibrated model is then used to quantitatively assess the dynamic and spatial consequences of demand and supply shifts. We find that nonhomotheticity in forms of income-elastic spending on housing/household durables and minimum structure requirement in housing production are essential ingredients

Real effects of money growth and optimal rate of inflation in a cash-in-advance economy with labor-market frictions

This paper studies the consequences of labor-market frictions for the real effects of steady inflation when cash is required for households' consumption purchases and firms' wage payments. Money growth may generate a positive real effect by encouraging vacancy creation and raising job matches. This may result in a positive optimal rate of inflation, particularly in an economy with moderate money injections to firms and with nonnegligible labor-market frictions in which wage bargains are not efficient. This main finding holds for a wide range of money injection schemes, with alternative cash constraints, and in a second-best world with pre-existing distortionary taxes