Essays on business cycles in Korea

Over the last two decades, a large amount of macroeconomic research has been directed towards the business cycle theory. Until now, however, most literature has focused on the business cycle research in the developed economies like the United States and European countries. On the other hand, the studies on emerging markets are very limited. From this perspective, this thesis attempts to contribute to the current literature by investigating the main characteristics of Korean business cycles, comparing its findings with the previous findings in the developed countries, and then drawing out the economic or policy implications. Another motivation of this thesis arises from the experience of the Korean financial crisis in the later half of 1997, which had a catastrophic impact on the Korean economy. Although it is not fully agreed on what caused the Korean financial crisis, there are a large amount of literature on this subject. However, what have not been dealt in literature is whether the Korean financial crisis brought out any noticeable changes on the fluctuations of key macroeconomic variables such as output, consumption, worked hours and asset wealth in Korea. One possible excuse for this scarcity is the limitation of data span, namely too short to analyze the difference between the pre- and post-crisis periods. It appears that as a decade passed, this is the right time to investigate this issue. Therefore, across three essays, this issue will be discussed with a high priority. With these two purposes in mind, this thesis starts by investigating the relationship among consumption, financial wealth and labor income with Korean data. This issue is discussed in the framework of the vector error correction model by applying the full information maximum likelihood approach suggested by Johansen (1988, 1995). The main finding from this analysis is that only financial wealth shows the sizable and statistically significant error correction behavior. This finding is also confirmed by the permanent and transitory component decomposition, which shows that only fluctuations of financial wealth are largely associated with transitory components while consumption and labor income are mainly governed by the permanent shocks during the examined period. By comparing the pre- and post-crisis periods, we also find that although there were several policy and institutional changes during the crisis, most adjustment to the long run relation has been done by financial wealth across the two sample periods. The second and last essays explore Korean business cycles by estimating the micro-founded dynamic stochastic general equilibrium models, using maximum likelihood and Bayesian approaches, respectively. Based on the estimation, the second essay finds that the estimated DSGE model out performs VAR models in predicting hours worked but it has difficulty in predicting other key macrovariables. In addition, although the volatility of the economy has decreased in the recent, the Korean financial crisis seemed not to change the deep parameters in the model. Finally; by comparing the second moments from the HP filtered data with those from the simulated data, this essay finds that the estimated model successfully reproduces the relative volatility of consumption and hours worked as well as the pattern of contemporaneous correlations of output with consumption, investment and hours worked. The last essay extends the baseline model in the second essay by introducing money through cash-in-advance constraints, that is, firms should borrow cash to pay wages in advance while households have to hold cash to purchase consumption goods. After estimating two versions of cash-in-advance models, namely a baseline cash-in-advance model and a limited participation model, this essay shows that the limited participation model is better to match up the stylized facts in Korean business cycles. In particular, it successfully captures the rise of output in response to an expansionary money shock. Finally, the comparison between the pre- and post crisis periods shows a sharp decline of money shock and a slight decline of productivity shock

Small solutions of the Einstein-Boltzmann-scalar field system with Bianchi symmetry

We show that small homogeneous solutions to the Einstein-Boltzmann-scalar field system exist globally towards the future and tend to the de Sitter solution in a suitable sense. More specifically, we assume that the spacetime is of Bianchi type I--VIII, that the matter is described by Israel particles and that there exists a scalar field with a potential which has a positive lower bound. This represents a generalization of the work [19], where a cosmological constant was considered, and a generalization of [16], where a spatially flat FLRW spacetime was considered. We obtain the global existence and asymptotic behavior of classical solutions to the Einstein-Boltzmann-scalar field system for small initial data.Comment: 42 page

Better quality estimation for low resource corpus mining

000000000000000000000000000000000000000000000000000000010241 - University of California, Berkeleyhttps://aclanthology.org/2022.findings-acl.45/First author draf

Neighborhood Noise

Listening to sounds in everyday life is an important factor in a human life. You can talk, listen to music, and enjoy nature through sound. However, due to adverse effect, listening to unwanted sounds continuously may cause noise-induced health disorders. Noise is an inevitable pollution factor in modern society, and its severity is increasing day by day. In addition, as the improvement of the economic level and the demand for the calm quality of life are increasing, the noise-related problem is emerging as a continuous social issue. Most of the problems associated with noise are mental, especially in developed countries, where social issues with the neighborhood noise are getting worse. The severity of noise-related problems is associated with the characteristics of noise, personal sensitivities, and vulnerable groups, but continued exposure can adversely affect not only health but also sociocultural, ethical, and economical aspects. However, the knowledge of the direct and indirect effects of noise pollution on health is still insufficient. Due to these limitations, it is difficult to establish reasonable standards for resolution and therefore requires more scientific research works

Impact of process parameter modification on poly(3-hexylthiophene) film morphology and charge transport

Organic electronics based on π-conjugated semi-conductor raises new technology, such as organic film transistors, e-paper, and organic photovoltaic cells that can be implemented cost-effectively on large-area applications. Currently, the device performance is limited by low charge carrier mobility. Poly(3-hexylthiophene) (P3HT) and organic field effect transistors (OFET) is used as a model to investigate morphology of the organic film and corresponding electronic properties. In this thesis, processing parameters such as boiling points and solubility are controlled to impact the micro- and macro-morphology of the film to enhance the charge transport of the device. Alternative approach to improve ordering of polymer chains and increase in charge transport without post-treatment of P3HT solution is studied. The addition of high boiling good solvent to the relatively low boiling main solvent forms ordered packing of π-conjugated polymers during the deposition process. We show that addition of 1% of dichlorobenzene (DCB) to the chloroform based P3HT solution was sufficient to improve wetting and molecular structures of the film to increase carrier mobility. Systematic study of solvent-assisted re-annealing technique, which has potential application in OFET encapsulation and fabrication of top-contact OFET, is conducted to improve mobility of OFET, and, to suggest a cost-effective processing condition suitable for industrial application. Three process parameters: boiling point, polarity, and solubility are investigated to further understand the trend of film response to the solvent-assisted technique. We report the high boiling non-polar solvents with relatively high RED values promote highest improvement in molecular packing and formulate crystalline structure of the thin film, which increases the device performance.M.S