974 research outputs found
China's Exports and Employment
No full textDooley et al (2003, 2004a,b,c) argue that China seeks to raise urban employment by 10-12 million persons per year, with about 30% of that coming from export growth. In fact, total employment increased by 7.5-8 million per year over 1997-2005. We estimate that export growth over 1997-2002 contributed at most 2.5 million jobs per year, with most of the employment gains coming from non-traded goods like construction. Exports grew much faster over the 2000-2005 period, which could in principal explain the entire increase in employment. However, the growth in domestic demand led to three-times more employment gains than did exports over 2000-2005, while productivity growth subtracted the same amount again from employment. We conclude that exports have become increasingly important in stimulating employment in China, but that the same gains could be obtained from growth in domestic demand, especially for tradable goods, which has been stagnant until at least 2002.
Domestic Value Added and Employment Generated by Chinese Exports: A Quantitative Estimation
No full textWe develop an input-output methodology to estimate how Chinese exports affect the country’s total domestic value added (DVA) and employment for 1995 and 2002. Total DVA generated by exports is obtained by subtracting all direct and indirect imported intermediate goods from the gross value of exports, and total employment is obtained by adding all direct and indirect employment generated by exports. To implement these estimations, we use hitherto unpublished Chinese government data to construct several completely new datasets, including an input-output table with separate input-output and employment-output coefficients for processing and non-processing exports. In 2002 (1995), for every US466 (US$545) and 0.242 (0.375) person-year, respectively.Input-output tables, Chinese exports, employment, domestic value added
Photoelectrocatalytic [4+2] Annulation for S‐Heterocycle Assembly Enabled by Proton‐Coupled Electron Transfer (PCET)
No full textCross‐dehydrogenative couplings (CDC) present an efficient strategy for the assembly of biorelevant heterocycles, but are thus far largely limited to toxic transition metals and rather harsh reaction conditions. In sharp contrast, we, herein report on a mild photoelectrocatalyzed CDC‐[4+2] annulation enabling the synthesis of functionalized isothiochromenes enabled by a proton‐coupled electron transfer (PCET) strategy. The transformative photoelectrocatalysis obviated toxic transition‐metal, high reaction temperatures, and stoichiometric chemical redox reagents. This approach was characterized by exceedingly mild conditions, ample substrate scope, and a commercially available catalyst. Gram‐scale reactions and a telescoped synthesis route reflected the unique potential in the green synthesis of important S‐heterocycles
Electrocatalyzed direct arene alkenylations without directing groups for selective late-stage drug diversification
No full textElectrooxidation has emerged as an increasingly viable platform in molecular syntheses that can avoid stoichiometric chemical redox agents. Despite major progress in electrochemical C−H activations, these arene functionalizations generally require directing groups to enable the C−H activation. The installation and removal of these directing groups call for additional synthesis steps, which jeopardizes the inherent efficacy of the electrochemical C−H activation approach, leading to undesired waste with reduced step and atom economy. In sharp contrast, herein we present palladium-electrochemical C−H olefinations of simple arenes devoid of exogenous directing groups. The robust electrocatalysis protocol proved amenable to a wide range of both electron-rich and electron-deficient arenes under exceedingly mild reaction conditions, avoiding chemical oxidants. This study points to an interesting approach of two electrochemical transformations for the success of outstanding levels of position-selectivities in direct olefinations of electron-rich anisoles. A physical organic parameter-based machine learning model was developed to predict position-selectivity in electrochemical C−H olefinations. Furthermore, late-stage functionalizations set the stage for the direct C−H olefinations of structurally complex pharmaceutically relevant compounds, thereby avoiding protection and directing group manipulations.Open-Access-Publikationsfonds 202
Towards a Local-Global Visual Feature-Based Framework for Recognition
No full textGeneral object and activity recognition is a fundamental problem in computer vision, which has been the subject of much research. Traditional approaches include model-based and appearance template-based methods. Recently, inspired by methods from the text retrieval literature, local visual feature-based models have shown a lot of success for recognition of objects or activities with large within-class geometric variability. There are several challenges in this approach, namely feature selection and target modeling using these features. This thesis proposes a local-global visual feature-based framework for general object and activity recognition with novel methods for these problems: 1) Combinatorial and statistical methods for selecting informative parts to build statistical models for part-based object recognition. First a combinatorial optimization formulation is used for clustering on a weighted multipartite graph. Second, a statistical method for selecting discriminative parts from positive images is used to localize objects. 2) An entropy based vocabulary selection method for “bag-of-words ” models for activity recognition. 3) Integrating both spatial and temporal information with appearance features for human activity recognition. This method models the human motions with the distribution of local motion features and their spatial-temporal arrangements. ii The effectiveness of the proposed methods is demonstrated by several object recognition and activity recognition data sets, which include human facial expressions and hand gestures, etc. This thesis also covers an interesting project regarding a framework of applying Discrete Fourier Transform to detect salient regions in images and video sequences. This framework generalizes the previous saliency detection methods and can be applied for saliency detection in the video sequences
Constructing tree decompositions of graphs with bounded gonality
No full textIn this paper, we give a constructive proof of the fact that the treewidth of a graph is at most its divisorial gonality. The proof gives a polynomial time algorithm to construct a tree decomposition of width at most k, when an effective divisor of degree k that reaches all vertices is given. We also give a similar result for two related notions: stable divisorial gonality and stable gonality.Accepted author manuscriptDiscrete Mathematics and Optimizatio
Physical Activities and Parkinson's Disease Progression: A Two‐Sample Mendelian Randomization Study
No full textABSTRACT Aims To explore the causal relationship between physical activity (PA) and the progression of Parkinson's disease (PD), we conducted a two‐sample Mendelian randomization (MR) analysis. Methods Genetic variants were obtained from publicly available genome‐wide association study (GWAS) summary statistics for PA ( N = 377,000), age at onset ( N = 28,568), and PD progression ( N = 4093). Causal estimates were calculated using the inverse variance weighted (IVW) method, with MR‐Egger and weighted median analyses performed to assess the robustness of the results. Results Genetically predicted accelerometer‐based overall acceleration average (OAA) was associated with a reduced risk of constipation in PD progression (OR: 0.60, 95% CI: 0.42–0.86, p = 5.50 × 10 −3 ). Moderate‐to‐vigorous physical activity (MVPA) demonstrated a similar but stronger effect on constipation risk (OR: 0.03, 95% CI: 9.38 × 10 −4 –0.90, p = 0.043). Additionally, OAA showed a protective effect on motor experiences of daily living (OR: 0.84, 95% CI: 0.71–1.00, p = 0.046). No causal effects were identified for vigorous physical activity (VPA) or the fraction of accelerations exceeding 425 milligravities (FAA) on PD progression. Conclusion Our findings suggest a negative causal relationship between PA and PD progression, highlighting the potential role of physical activity in guiding therapeutic strategies for PD management
Mechanical and Structural Properties of Microwave Sintered Tin-Copper-Antimony Alloys
No full textTin-copper-antimony (pewter) alloys have been traditionally produced by a casting process which consumes large amounts of energy, time and as a result is expensive. This research aims to investigate the possibilities of implementing powder metallurgy for pewter production through a sintering process using microwave energy. The optimum sintering conditions using microwave sintering are also of interest. Pewter alloys were examined to determine the effect of green density, sintering time, and sintering temperature on the mechanical and structural properties of the sintered compacts. Samples were prepared by hydraulic pressing of a well mixed and blended tin alloy powder with three different compositions; 97wt%Sn 2wt%Cu 1wt%Sb, 94wt%Sn 4wt%Cu 2wt%Sb and 91wt%Sn 6wt%Cu 3wt%Sb. Two compaction loads were used to produce the samples with different green densities. Pellets pressed at 96 MPa had an average relative density of 80.7%, while those pressed at 129 MPa had an average green density of 84.6%.
Sixteen different time-temperature combinations were used for the heat treatments at 160 and 220 C for both conventional and microwave sintering. However, the sintering times had to be restricted to 15 and 30 minutes for microwave heating. Meanwhile, 60 and 120 minutes were used for conventional heating. It was found that for all three compositions, samples with a higher green density had a higher sintered density, compared to samples with lower green density, for the same sintering time and temperature. The relative density of sintered pewter alloys increased on average by 13% after conventional sintering and by about 14% after microwave sintering, when the sintering was carried out for the longer of the two sintering times and at the higher of the sintering temperatures selected, for all three compositions.
Moreover, the hardness increased by 25.6%, 23.5% and 7.0% when microwave sintered relative to the conventional sintering for 97Sn2Cu1Sb, 94Sn4Cu2Sb and 91Sn6Cu3Sb alloys respectively. Nevertheless, the grain size remained similar for all three compositions under the same sintering conditions. The degree of grain growth in microwave sintered samples was marginally smaller (up to 23-24 μm) than in conventionally sintered samples which reached a grain size of 26-27 μm.
In terms of strength, microwave sintering produced samples with similar properties to those conventionally sintered under the same sintering conditions for all three compositions. The tensile strengths obtained compared well with the strengths obtained from the casting process. Nonetheless, tensile strengths for both conventionally and microwave sintered material was higher in the transverse direction than in the longitudinal direction. In conventionally sintered material, there was an increase in transverse strength of about 6.9%, 5% and 4%, while for the microwave sintered material, the strength increase was 9.1%, 5.6% and 4.5% for 97Sn2Cu1Sb, 94Sn4Cu2Sb and 91Sn6Cu3Sb alloys respectively when compared to the longitudinal direction.
The microwave sintered samples in general have improved hardness, better densification and a finer microstructure compared with the conventionally sintered samples and traditionally cast pewter. Increasing the Cu and Sb content increases the hardness and strength but in return, decreases its ductility. Hence, a pewter alloy with a moderate amount of Cu and Sb, i.e. 97Sn2Cu1Sb, microwave sintered at 220 C for 30 minutes would be the best choice for optimum mechanical properties
Shui zai bu tong wen du xia de jie gou yan bian he gou jian xin qi li wang jie gou
No full textPh.D.Water is the most common and important liquid in our life and plays an indispensable role in physical, chemical, biological, ecological and geological processes. However, we haven’t known everything about it since it shows lots of anomalies in its properties. The best-known is the maximum in density at 4℃ at atmospheric pressure. Correspondingly, simple liquids have a monotonous relationship between their density and temperature. Water’s other properties such as isobaric heat capacity, thermal expansion coefficient, isothermal compressibility also exhibit abnormal behaviors. These anomalous properties are usually thought to be related to the intermolecular network of hydrogen bonds (H-bonds) in liquid water. In my experiment, a 30 Hz area detector was used to collect the X-ray diffraction data of a drop of deionized water during its freezing process. And the diffraction data of stable water at different temperatures were also collected. We can learn how water’s structure evolves when the temperature changes by analyzing the diffraction images. At the same time, we use molecular dynamics (MD) simulation to calculate the simulated diffraction intensity and compare it with the real experiment. Several different water models were tested, and the TIP4P-Ew model’s results agree well with our experiment. We can distinguish two types of water by their different structures. Combining the experiment and simulation results, the fraction of the two types of water and the fraction of ice when water freezes can be calculated. This method offers a new way to estimate the fraction of two types of water from real experiment results.Mechanical metamaterials are a type of artificialities with abnormal properties that hard to be found in natural materials, such as negative Poisson’s ratio, negative compressibility, vanishing modulus, singularly nonlinear, and ultra-stiff. These fancy properties usually originate from their structures, instead of their compositions. Natural materials generally have regular structures, on the contrary most of the metamaterials exhibiting abnormal properties possess disordered structures, such as jamming networks. However, by randomly displacing the nodes of a crystalline, the newly generating central force network exhibiting strange property, i.e. negative Poisson’s ratio. Going a step further, by removing shorter or longer bonds, the Poisson’s ratio of this novel force network will decrease or increase correspondingly. We design a unit cell having a wide range of Poisson’s ratio, and the unit cell assembly is expected to have similar properties with the unit cell. Therefore, arbitrary size and wide range Poisson’s ratio metamaterials can be designed, which are expected to have many applications in various fields.水在我們生活中是一種最常見也最重要的液體，在諸多物理、化學、生物、生態和地質過程中發揮著不可或缺的作用。然而，對於水我們並非完全瞭解，因爲它有著太多反常的性質。其中最著名的是在正常大氣壓下，水在4攝氏度時密度最大。與之相對應的是，簡單液體的密度和溫度通常是單調的關系。水的其他性質例如等壓熱容、熱膨脹系數、等溫壓縮率等都展現出了反常的性質。這些反常的性質通常被認爲與液態水中大量存在的分子間的氫鍵形成的網絡有關。在我的實驗中，我們使用一個最快拍照速度爲每秒30張的區域探測器來收集水在結冰過程中的X射線衍射圖像。不同溫度條件下穩態水的衍射圖像也被測量收集。通過分析在不同溫度下水的衍射圖像我們可以瞭解水的結構如何演化。同時，我們使用分子動力學模擬的方法來模擬水的X射線衍射強度並將其與實驗對比。我們選用了多個不同的水模型，其中TIP4P-Ew模型模擬出的結果與我們實驗吻合得較好。我們可以通過兩種不同的結構劃分出兩種類型的水。結合實驗和模擬的結果，不同條件下這兩種水以及水在結冰過程中的冰的比例都可以計算得到。這種方法提供了一種從實驗中直接得到兩種水比例的新思路。力學超構材料是一類具有反常性質例如：負泊松比、負壓縮率、零模量、奇異非線性和超強硬度等的材料，這種材料通常是人爲設計，自然界很難找到。這些奇特的性質通常是源於它們的結構而非組成成分。自然界中的材料通常有着規則的結構，因此與之相反的是，展現出反常性質的超構材料一般有着無序的結構，例如一些阻塞結構網絡。然而，通過隨機扭曲晶體結構的節點位置，新生成的中心力網絡展現出了奇特的性質，即負泊松比。更進一步，通過去掉短或者長的連接，這種中心力網絡結構的泊松比將會相應地減小或者增大。由此我們設計了一種具有廣泛可調的泊松比的單元，這些單元的組合同樣保持與單元相同的性質。因此我們可以設計任意尺寸的具有可調泊松比的超構材料，這種材料在衆多領域都可能有廣泛的應用。Jin, Zhipeng = 水在不同温度下的結構演變和構建新奇力網結構 / 金志鵬.Thesis Ph.D. Chinese University of Hong Kong 2019.Includes bibliographical references (leaves 78-92).Abstracts also in Chinese.Title from PDF title page (viewed on 26, March 2021).Jin, Zhipeng = Shui zai bu tong wen du xia de jie gou yan bian he gou jian xin qi li wang jie gou / Jin Zhipeng
- …
