MEASURING INTERACTIONS AMONG URBAN DEVELOPMENT, LAND USE REGULATIONS, AND PUBLIC FINANCE

In this paper, a theoretical model is developed to analyze the interactions among residential development, land use regulations, and public financial impacts (public expenditure and property tax). A simultaneous equations system with self-selection and discrete dependent variables is estimated to determine the interactions for counties in the five western states (California, Idaho, Nevada, Oregon, and Washington). The results show that county governments are more likely to impose land use regulations when facing rapid land development, high public expenditure and property tax. The land use regulations, in turn, decrease land development, long-run public expenditure, and property tax at the cost of higher housing prices and property tax. During the period of 1982-1992, land use regulations reduced developed areas by 612,800 acres or 8.8 % of the developed area of five western states in 1992, but increased housing price by $5,741 per unit under "stringent" regulations and$1,319 per unit under "low" regulations. Because it costs money to develop and implement land use regulations, land use regulations increased public expenditure and property tax in the short run, during the period of 1982-1987. However, in the long-run (1982-1992), land use regulations actually reduce public expenditure and property taxes because the regulations reduce developed areas. The results also show that land use regulations, land development, public expenditure, and property tax all are significantly affected by population, geographic location, land quality, housing prices, and the risks and costs of development.Community/Rural/Urban Development, Land Economics/Use,

Endogenous Income Distribution with Product Obsolescence

Wage inequality in U. S. and UK has increased over the past 25 years. Paradoxically, skilled labor supply has also increased in both countries. This paper develops the dynamic general equilibrium model of product innovation with product obsolescence. We develop a model to provide an explanation of inequality phenomena between skilled and unskilled labor by the channel of innovation and market structure. This paper builds on the dynamic general equilibrium model of product innovation and incorporates overhead cost of the production of intermediate goods to capture endogenous growth rate of innovation, hazard rate, product life cycle and inequality.wage inequality, skilled and unskilled labor, product innovation, general equilibrium

Public Expenditure and Poverty Reduction in the Southern United States

The objective of this research was to analyze the effects of education, health and hospital, parks and recreation, and public welfare expenditures on poverty, focusing particularly on how these relationships change over space and time. Government expenditure on parks and recreation has been the single most effective government expenditure category over time, although the marginal effects of the government expenditure on poverty alleviation have weakened over time. Clusters of the highest marginal effects of government expenditures on poverty reduction were identified for each time period using geographically weighted regression (GWR) and analysis of local indicators of spatial association (LISA)government expenditure, GWR, poverty, southern United States, Community/Rural/Urban Development,

Development of Organic Semiconductors for Soft Electronics

Organic semiconductors, Soft electronics, Colloid, Mini-emulsion synthesis, Breath-figure moldingOrganic semiconductor based soft electronic devices are demonstrated: (1) effects of conjugation length on charge transport in polymer semiconductors, (2) water-borne colloids of organic semiconductors, and (3) breath-figure molding of polymer semiconductors for sensors. To improve the charge carrier mobility of diketopyrrolopyrrole donor-acceptor copolymer semiconductors, the length of the donor building block is controlled using vinylene moieties, and its effects on crystalline structure and charge transport are systematically studied. We synthesize P29-DPP-TBT with two vinylene linkages between thiophene units and compare it with P29-DPP-TVT with single vinylene linkage. Density functional theory calculations predict enhanced backbone planarity of P29-DPP-TBT compared to P29-DPP-TVT, which can be related with the increased conjugation length of P29-DPP-TBT as proved by the increased free exciton bandwidth extracted from UV-vis absorption spectra and the wavenumber shift of the C–C peaks to higher values in Raman spectra. From two-dimensional grazing incident X-ray diffraction studies, it is turned out that the paracrystalline disorder is lower in P29-DPP-TBT than in P29-DPP-TVT. Near-edge X-ray absorption fine structure spectroscopy reveal that more edge-on structure of polymer backbone is formed in the case of P29-DPP-TBT. By measuring the temperature-dependence of the charge carrier mobilities, it is turned out that the activation energy for charge hopping is lower for P29-DPP-TBT than for P29-DPP-TVT. Collectively, these results imply that the substitution of extended π-conjugated donor moiety of polymeric semiconductors can yield a more planar backbone structure and thus enhanced intermolecular interaction which enables more perfect crystalline structure as well as enhanced charge transport behavior. A synthetic approach has demonstrated to enhance coalescence phenomenon during solidification of water-borne colloids so that thin, even, and continuous film morphology of polymer semiconductors can be realized. From theoretical study of complex colloids, it is shown that small-sized and uniform colloid particles are essential to minimize depletion contact energy between colloid particles and thus to enhance coalescence. Therefore, the newly synthesized polymer semiconductor is designed for better molecular affinity with surfactants, so that phase transfer of polymer semiconductors from organic phase to water phase can proceed more efficiently during mini-emulsion synthesis. This is achieved by substituting a Si atom to the branching C atom of the alkyl solubilizing group of a conventional donor-acceptor polymer semiconductor. Such a chemical modification increases the volumetric portion of hydrophobic alkyl chains and thus enables higher solu-bility as well as higher hydrophobicity, all of which are closely related with enhancing molecular affinity be-tween polymer semiconductor and surfactants. As a result, the performance of organic field-effect transistors fabricated from water-borne colloids can be improved to a level similar to the case of organic solvents. More importantly, the reproducibility of transistor performance is also greatly improved due to the small and uni-form water-borne colloidal particles. Strategically designed polymer semiconductor thin film morphology with both high responsivity to the specific gas analyte and high signal transport efficiency is reported to realize high-performance flexible NOx gas sensors. Breath-Figure (BF) molding of polymer semiconductors enables a finely defined degree of nano-porosity in polymer films with high reproducibility while maintaining a high charge carrier mobility characteristics of organic field effect transistors (OFETs). The optimized BF-OFET with a donor-acceptor copolymer exhibits a maximum responsivity of over 104%, sensitivity of 774%/ppm, and limit of detection (LOD) of 110 ppb against NO. When tested across at NO concentrations of 0.2–10 ppm, the BF-OFET gas sensor ex-hibits a response time of 100–300 s, which is suitable for safety purposes in practical applications. Further-more, BF-OFETs show a high reproducibility as confirmed by statistical analysis on 64 independently fabri-cated devices. Selectivity to NOx analytes is tested by comparing the sensing ability of BF-OFET to other re-ducing gases and volatile organic compounds. Finally, flexible BF-OFETs conjugated with plastic substrates are demonstrated and they exhibit a sensitivity of 500%/ppm and LOD of 215 ppb, with a responsivity degradation of only 14.2% after 10,000 bending cycle at 1% strain.YPart Ⅰ. Effects of conjugation length on crystalline perfectness and charge transport in diketopyrrolopyrrole-based polymer semiconductors 1 Ⅰ. Introduction 2 Ⅱ. Experimental Section 3 2.1 Materials 3 2.2 Device fabrication 3 2.3 Characterization 4 2.4 Measurements 4 Ⅲ. Results and Discussions 5 Ⅳ. Conclusion 13 Ⅴ. References 14 Part Ⅱ. Facilitating Phase Transfer of Polymer Semiconductor in Mini-Emulsion Synthesis via Molecular Affinity Engineering 18 Ⅰ. Introduction 19 Ⅱ. Experimental Section 21 2.1 Materials 21 2.2 Colloid synthesis 21 2.3 Device fabrication 21 2.4 Characterization 21 2.5 Measurements 22 Ⅲ. Results and Discussions 22 3.1 Efficiency of Mini-emulsion 22 3.2 Film Morphology 26 3.3 Crystallinity and Molecular Orientation 28 3.3 Electrical Properties of Organic Field-effect Transistors (OFETs) 30 Ⅳ. Conclusion 32 Ⅴ. References 33 Part Ⅲ. Breath-Figure Molding of Polymer Transistors to Implement Flexible and High-Performance NOx Sensors 36 Ⅰ. Introduction 37 Ⅱ. Experimental Section 39 2.1 Device fabrication 39 2.2 Film characterization 39 2.3 Measurements 40 Ⅲ. Results and Discussions 40 Ⅳ. Conclusion 50 Ⅴ. References 51 국문요약 55본 논문은 유기 반도체를 이용한 유연 소자 개발 방법들을 제시한다: (1) 고분자 반도체의 공액 길이에 따른 전하 이동 영향, (2) 수분산 유기 반도체 콜로이드 합성 및 이를 이용한 소자 개발, (3) breath-figure 패턴 몰딩법을 이용한 센서 개발. 디케토피롤로피롤(diketopyrrolopyrrole) 전자 주개-받개 구조의 공중합체 반도체의 전하 운반체 이동성을 향상시키기 위해, 주개 구조의 길이는 비닐렌 단위체를 사용하여 제어된 채 결정 구조 및 전하 수송에 미치는 영향을 체계적으로 연구한다. 티오펜 단위체 사이에 2 개의 비닐렌 결합을 갖는 P29-DPP-TBT를 합성하고 단일 비닐렌 결합을 갖는 P29-DPP-TVT와 비교한다. 분자 이론 계산을 통하여 P29-DPP-TVT와 비교하여 P29-DPP-TBT의 향상된 백본 평면성을 예측하고, 자외선-가시광선 흡광 스펙트럼과 라만 스펙트럼을 이용하여 추출된 자유 엑시톤 대역폭이 증가함에 따라 P29-DPP-TBT의 공액 길이가 길어짐을 증명한다. 2 차원 X- 선 회절 분석법을 이용하여, P29-DPP-TVT보다 P29-DPP-TBT에서 결정성이 뛰어남을 확인하였다. 추가적으로, X- 선 흡수 미세 구조 분광법에서 P29-DPP-TBT의 경우에 고분자 백본이 더 많은 에지-온 구조로 형성됨을 보여준다. 전하이동도의 온도 의존성을 측정함으로써, 전하 호핑을 위한 활성화 에너지는 P29-DPP-TVT보다 P29-DPP-TBT에 대해 더 낮은 것으로 밝혀졌다. 종합적으로, 이들 결과는 공중합체 고분자 반도체의 연장된 π- 공액 전자 주개 부분의 치환이 보다 평면적 인 골격 구조를 생성할 수 있고, 이에 따라 보다 완전한 결정질 구조 및 향상된 전하 수송 거동을 가능하게 하여 분자간 상호 작용을 향상시킬 수 있음을 의미한다. 고분자 합성 측면에 있어 수성 콜로이드의 박막화 동안 응축 현상을 향상시켜서, 고분자 반도체의 얇고 균일하며 연속적인 박막 형태가 실현될 수 있음을 입증하였다. 콜로이드에 대한 이론적 연구로, 크기가 작고 균일한 콜로이드 입자가 콜로이드 입자 사이의 공핍 접촉 에너지를 최소화하고 따라서 응축을 향상시키는 데 필수적이라는 것이 밝혀졌다. 따라서, 새롭게 합성된 공중합체 고분자 반도체는 계면활성제와의 분자 친화성이 향상되도록 설계되어, 유기상으로부터 수상으로 공중합체 고분자 반도체의 상 전이가 미니-에멀젼 합성 동안 보다 효율적으로 진행될 수 있다. 이는 통상적인 전자 주개-받개 구조의 공중합체 고분자 반도체의 알킬 체인 그룹의 분 지형 C 원자에 Si 원자를 치환함으로써 가능하게 하였다. 이러한 화학적 변형은 소수성 알킬 체인의 부피를 증가시키고 따라서 더 높은 용해도 및 더 높은 소수성을 가능하게 하며, 이는 모두 공중합체 고분자 반도체와 계면활성제 사이의 분자 친화도를 향상시키는 것과 밀접한 관련이 있다. 결과적으로, 수계 콜로이드로 제조된 유기 전계 효과 트랜지스터의 성능은 유기 용매의 경우와 유사한 수준으로 개선될 수 있음을 입증하였다. 더불어 작고 균일한 수성 콜로이드 입자로 인해 박막 트랜지스터 성능의 재현성이 크게 향상된다. 특정 가스 분석 물질에 대한 높은 반응성과 높은 신호 전송 효율을 모두 갖춘 고분자 반도체 박막 모폴로지를 구현함으로써, 고성능의 유연한 NOx 가스 센서를 실현하였다. 고분자 반도체의 Breath-Figure (BF) 몰딩은 유기 전계 효과 트랜지스터 (OFET)의 높은 전하 캐리어 이동 특성을 유지하면서 고분자 박막에서 미세한 크기의 나노 다공성 표면 개질을 가능하게 하였다. 전자 주개-받개 구조의 공중합체 기반의 최적화된 BF-OFET는 최대 104 % 이상의 반응성과, 774% / ppm의 감도 및 NO에 대한 110 ppb의 검출 한계 (LOD)를 나타낸다. 0.2 ~ 10ppm의 NO 농도에서 측정시에 BF-OFET 가스 센서는 100 ~ 300 초의 응답 시간을 나타내며 이는 실제 응용 소자로 쓰일 수 있는 수준이다. 또한, BF-OFET는 64 개의 독립적으로 제조된 소자에 대한 통계 분석에 의해 확인 된 바와 같이 높은 재현성을 나타낸다. NOx 가스에 대한 선택성은 BF-OFET의 감지 능력을 다른 환원 가스 및 휘발성 유기 화합물과 비교하여 측정하였다. 최종적으로 플라스틱 기판과 접합된 유연한 BF-OFET을 구현하였으며 이 소자는 1% 변형률에서 10,000 회 굽힘 주기 후 14.2%의 응답성 저하를 보였으며, 500 % / ppm의 감도와 215ppb의 LOD를 나타냈다.MasterdCollectio

BANDWIDTH SELECTION FOR SPATIAL HAC AND OTHER ROBUST COVARIANCE ESTIMATORS

This research note documents estimation procedures and results for an empirical investigation of the performance of the recently developed spatial, heteroskedasticity and autocorrelation consistent (HAC) covariance estimator calibrated with different kernel bandwidths. The empirical example is concerned with a hedonic price model for residential property values. The first bandwidth approach varies an a priori determined plug-in bandwidth criterion. The second method is a data driven cross-validation approach to determine the optimal neighborhood. The third approach uses a robust semivariogram to determine the range over which residuals are spatially correlated. Inference becomes more conservative as the plug-in bandwidth is increased. The data-driven approaches prove valuable because they are capable of identifying the optimal spatial range, which can subsequently be used to inform the choice of an appropriate bandwidth value. In our empirical example, pertaining to a standard spatial model and ditto dataset, the results of the data driven procedures can only be reconciled with relatively high plug-in values (n0.65 or n0.75). The results for the semivariogram and the cross-validation approaches are very similar which, given its computational simplicity, gives the semivariogram approach an edge over the more flexible cross-validation approach.spatial HAC, semivariogram, bandwidth, hedonic model

COMMUNITY CHOICES AND HOUSING DECISIONS: A SPATIAL ANALYSIS OF THE SOUTHERN APPALACHIAN HIGHLANDS

This paper examines land development using an integrated approach that combines residential decisions about choices of community in the Southern Appalachian region with the application of the GIS (Geographical Information System). The empirical model infers a distinctive heterogeneity in the characteristics of community choices. The results also indicate that socioeconomic motives strongly affect urban housing decisions while environmental amenities affect those of rural housing.Public Economics,