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  • 1
    Language: English
    In: Soil Biology and Biochemistry, February 2011, Vol.43(2), pp.333-338
    Description: Changes in the soil water regime, predicted as a consequence of global climate change, might influence the N cycle in temperate forest soils. We investigated the effect of decreasing soil water potentials on gross ammonification and nitrification in different soil horizons of a Norway spruce forest and tested the hypotheses that i) gross rates are more sensitive to desiccation in the Oa and EA horizon as compared to the uppermost Oi/Oe horizon and ii) that gross nitrification is more sensitive than gross ammonification. Soil samples were adjusted by air drying to water potentials from about field capacity to around −1.0 MPa, a range that is often observed under field conditions at our site. Gross rates were measured using the N pool dilution technique. To ensure that the addition of solute label to dry soils and the local rewetting does not affect the results by re-mineralization or preferential consumption of N, we compared different extraction and incubation times. T times ranging from 10 to 300 min and incubation times of 48 h and 72 h did not influence the rates of gross ammonification and nitrification. Even small changes of water potential decreased gross ammonification and nitrification in the O horizon. In the EA horizon, gross nitrification was below detection limit and the response of the generally low rates of gross ammonification to decreasing water potentials was minor. In the Oi/Oe horizon gross ammonification and nitrification decreased from 37.5 to 18.3 mg N kg  soil d and from 15.4 to 5.6 mg N kg  soil d when the water potential decreased from field capacity to −0.8 MPa. In the Oa horizon gross ammonification decreased from 7.4 to 4.0 mg N kg  soil d when the water potential reached −0.6 MPa. At such water potential nitrification almost ceased, while in the Oi/Oe horizon nitrification continued at a rather high level. Hence, only in the Oa horizon nitrification was more sensitive to desiccation than ammonification. Extended drought periods that might result from climate change will cause a reduction in gross N turnover rates in forest soils even at moderate levels of soil desiccation. ► Even small changes of water potential decreased gross N turnover rates in the O horizon. ► Only in the Oa horizon gross nitrification was more sensitive to desiccation than ammonification. ► A reduction in gross N turnover rates can be expected in forest soils even at moderate desiccation.
    Keywords: 15n Pool Dilution Technique ; Norway Spruce ; Forest Soil ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 2
    Language: English
    In: Soil biology & biochemistry, 2011, Vol.43, pp.333-338
    Description: Changes in the soil water regime, predicted as a consequence of global climate change, might influence the N cycle in temperate forest soils. We investigated the effect of decreasing soil water potentials on gross ammonification and nitrification in different soil horizons of a Norway spruce forest and tested the hypotheses that i) gross rates are more sensitive to desiccation in the Oa and EA horizon as compared to the uppermost Oi/Oe horizon and ii) that gross nitrification is more sensitive than gross ammonification. Soil samples were adjusted by air drying to water potentials from about field capacity to around −1.0 MPa, a range that is often observed under field conditions at our site. Gross rates were measured using the 15N pool dilution technique. To ensure that the addition of solute label to dry soils and the local rewetting does not affect the results by re-mineralization or preferential consumption of 15N, we compared different extraction and incubation times. T0 times ranging from 10 to 300 min and incubation times of 48 h and 72 h did not influence the rates of gross ammonification and nitrification. Even small changes of water potential decreased gross ammonification and nitrification in the O horizon. In the EA horizon, gross nitrification was below detection limit and the response of the generally low rates of gross ammonification to decreasing water potentials was minor. In the Oi/Oe horizon gross ammonification and nitrification decreased from 37.5 to 18.3 mg N kg−1 soil d−1 and from 15.4 to 5.6 mg N kg−1 soil d−1 when the water potential decreased from field capacity to −0.8 MPa. In the Oa horizon gross ammonification decreased from 7.4 to 4.0 mg N kg−1 soil d−1 when the water potential reached −0.6 MPa. At such water potential nitrification almost ceased, while in the Oi/Oe horizon nitrification continued at a rather high level. Hence, only in the Oa horizon nitrification was more sensitive to desiccation than ammonification. Extended drought periods that might result from climate change will cause a reduction in gross N turnover rates in forest soils even at moderate levels of soil desiccation. ; Includes references ; p. 333-338.
    Keywords: Forest Soils ; Coniferous Forests ; Soil Water Content ; Detection Limit ; Acid Soils ; Forest Trees ; Climate Change ; Drought ; Ammonification ; Nitrogen ; Biogeochemical Cycles ; Soil Horizons ; Nitrification ; Soil Water Regimes ; Mineralization ; Picea Abies ; Temperate Forests ; Soil Water Potential ; Soil Desiccation
    ISSN: 0038-0717
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 3
    Language: English
    In: Wetlands, 2012, Vol.32(3), pp.579-587
    Description: Changes of water table level and oxygen supply affect the nitrogen (N) and carbon (C) mineralization of fen soils with potential consequences for the N and C sink and sources function of fens. Here we studied the response of gross N mineralization and CO 2 emissions to water table fluctuations in an acidic minerotrophic fen. In a laboratory study lasting 117 days, undisturbed soil cores were either a) permanently flooded or b) subject to flooding, water table drawdown and reflooding. In the permanently flooded cores the CO 2 emissions were constantly low, but gross ammonification and immobilization of NH 4 + increased after a lag phase of about 30 and 70 days, respectively. In the fluctuated cores, gross ammonification and NH 4 + immobilization first remained constant but then increased after water table drawdown of 30 days. Emission of CO 2 peaked immediately after water table drawdown, followed by a decrease and a second maximum after about 30 days. Following re-flooding, gross ammonification and immobilization of NH 4 + first decreased but recovered after about 30 days to the level of the permanently flooded cores. In contrast, the CO 2 emissions decreased immediately and permanently after re-flooding. The cumulative gross ammonification was larger in the permanently flooded cores than in the fluctuated cores. Rates of gross nitrification and immobilization of NO 3 − were generally low and did not respond to the treatments. The ratios of CO 2 emission/gross ammonification were in the range of 1 to 4 under anoxic condition which seems to be caused by fast N turnover in the microbial biomass pool and low rates of C-mineralization of soil organic matter. Our results indicate that water table fluctuations in fen soils affect N and C mineralization differently. Changes of water table of a few days likely have a bigger effect on C-mineralization than on gross N mineralization.
    Keywords: Gross ammonification ; C mineralization ; Wetland ; Fen soil ; Water table
    ISSN: 0277-5212
    E-ISSN: 1943-6246
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  • 4
    Language: English
    In: Advances in Mechanical Engineering, 17 April 2015, Vol.7(4)
    Description: A numerical investigation into the initial stress distribution induced within the periodontal ligament by thermoplastic appliances with different thicknesses is performed. Based on the plaster model of a 25-year-old male patient, a finite element model of the maxillary lateral incisors and their supporting structures is constructed. In addition, four finite element models of thermoplastic appliances with different thicknesses in the range of 0.5–1.25 mm are also constructed based on the same plaster model. Finite element analysis simulations are performed to examine the effects of the force delivered by the thermoplastic appliances on the stress response of the periodontal ligament during the elastic recovery process. The results show that the stress induced in the periodontal ligament increases with an increasing appliance thickness. For example, the stress triples from 0.0012 to 0.0038 MPa as the appliance thickness is increased from 0.75 to 1.25 mm. The results presented in this study provide a useful insight into as a result of the compressive and tensile stresses induced by thermoplastic appliances of different thicknesses. Moreover, the results enable the periodontal ligament stress levels produced by thermoplastic appliances of different thicknesses to be reliably estimated.
    Keywords: Finite Element Analysis ; Thermoplastic Appliance ; Periodontal Ligament ; Elastic Recovery ; Engineering
    E-ISSN: 1687-8140
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  • 5
    Language: English
    In: Environmental Science and Pollution Research, 2017, Vol.24(1), pp.578-590
    Description: A previous study has demonstrated that Danshui River has almost the highest dissolved inorganic nitrogen (DIN) yield in the world and exports most of the DIN in the form of ammonium unlike the world’s large rivers. However, the DIN sources are poorly constrained. In this study, the contributions of major sources in the Taipei metropolitan area to the DIN export in the Danshui River were investigated. It is observed that ammonium is the major DIN species in the downstream reaches, resulting from the ammonium-dominated inputs of the effluents of wastewater treatment plants (WWTP) and rain water pumping stations (RWPS). DIN concentrations in the downstream (urban) reaches are substantially elevated. The upstream tributaries annually discharge ∼2709 t DIN to the downstream reaches. However, the DIN discharge off the downstream reaches rises to ∼17,918 t, resulting from the contribution of RWPS-collected water, i.e., ∼14,632 t, and the effluents of two WWTP, i.e., ∼577 t. RWPS-collected water inherently contains the contribution of atmospheric deposition, ∼2937 t DIN. This finding implies that ∼11,695 t (∼66 % of the downstream output) DIN flux off the Danshui River is from urban runoff and can be attributed to human activities in the Taipei metropolitan area. To improve the water quality in the Danshui River, water quality controls in urban runoff are important.
    Keywords: Rain water pumping station ; Wastewater treatment plant ; Water pollution control ; Urban runoff ; Nonpoint source pollution ; Urbanization
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 6
    Language: English
    In: Asia Pacific Journal of Clinical Nutrition, Vol. 20, No. 2, 2011: 301-308
    Description: Hyperuricemia is a recognized risk factor for cardiovascular disease. This study investigated trends in uric acid levels, hyperuricemia and gout among adults in Taiwan from 1993-1996 to 2005-2008, using data collection from, Nutrition and health surveys in Taiwan (NAHSIT) conducted in 1993-1996 and 2005-2008. Information on food frequency, medical history, physical measures and fasting blood parameters were analyzed. Mean uric acid levels decreased between 1993-1996 and 2005-2008 in both genders (6.77 vs 6.59 mg/dL in men and 5.33 vs 4.97 mg/dL in women) and the prevalence of hyperuricemia declined from 25.3% to 22.0% in men (p〈0.0001) and from 16.7% to 9.7% in women (p〈0.0001). However, the prevalence of gout (self-reported) increased (4.74% vs 8.21% in men and 2.19% vs 2.33% in women, p〈0.0001).Reduced rank regression was used to identify dietary patterns that explained significant amounts of variance in uric acid. Frequency of consumption of lean meat, soy products and soymilk, milk, eggs, vegetables, carrots, mushrooms, fruit and coffee were negatively associated with hyperuricemia, whereas consumption of organ meats, bamboo shoots, and soft drinks were positively associated with hyperuricemia. The dietary factor score (DFS) composed of the frequency of above food items decreased from -5.40 to -6.00 between the two surveys (p〈0.0001). In conclusion, uric acid levels and prevalence of hyperuricemia both declined, whilst self-reported gout increased between 1993-1996 and 2005-2008. Changes in dietary patterns may in part explain the decrease in uric acid levels between the two national surveys.
    Keywords: Health Surveys ; Nutrition--Evaluation ; Gout--Diet Therapy ; Hyperuricemia ; Uric Acid--Metabolism
    ISSN: 0964-7058
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  • 7
    Language: English
    In: IEEE Transactions on Industrial Electronics, September 2011, Vol.58(9), pp.4130-4135
    Description: A compact-size and high-conversion-efficiency regulator used to stabilize the luminous flux of alternating-current-operated light-emitting diodes (ACOLEDs) is proposed. The presented regulator is composed of a full-bridge rectifier and a power switch to supply directly from ac power source for the ACOLEDs without any ac/dc converter. Commonly adopted pulsewidth modulation techniques are utilized to regulate the input power fed into ACOLEDs. Design guidelines and experimental results of the prototyping regulator for an 8-W ACOLED operating under different input ac voltages (110 ±10 V〈sub〉rms〈/sub〉, 60 Hz) are provided. According to the experimental results, the advantages of the proposed regulator include simplified design, compact size, high conversion efficiency, and low cost. Since no magnetic component is required in the presented system, therefore, it can easily be fabricated into the same ACOLED chip in the future.
    Keywords: Resistors ; Regulators ; Light Emitting Diodes ; Voltage Control ; Lighting ; Pulse Width Modulation ; Threshold Voltage ; Alternating-Current-Operated Light-Emitting Diodes (Acoled) ; Pulsewidth Modulation (Pwm) ; Regulator ; Engineering
    ISSN: 0278-0046
    E-ISSN: 1557-9948
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  • 8
    Language: English
    In: Applied Sciences, 01 March 2017, Vol.7(3), p.279
    Description: Motorcycle helmets are essential for reducing the risk of head injuries in the event of an impact. However, during the design of helmets, a compromise must be made between user safety and user comfort. Accordingly, the present study proposes a novel open-face helmet design, in which the helmet...
    Keywords: Finite Element Analysis ; Motorcycle Helmet ; Impact Severity ; Head Injury ; Safety ; Engineering ; Sciences (General)
    E-ISSN: 2076-3417
    Source: Directory of Open Access Journals (DOAJ)
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  • 9
    Description: 博士 國立中正大學 機械工程系研究所 105 This article the application of computational biomechanics to the simulation of contact mechanics as relevant to the study of thermo-plastic and helmet. A numerical investigation is performed into the in-itial stress dis-tribution induced within the periodontal ligament (PDL) by thermo-plastic appliances with different thicknesses. Based on the plaster model of a 25-year-old female patient. The results presented in this study provide a useful insight into as a result of the compressive and tensile stresses induced by thermo-plastic appliances of different thicknesses. Motorcycle helmets are essential for reducing the risk of head in-juries in the event of an impact. However, during the design of hel-mets, a compromise must be made between user safety and user com-fort. FEA models were constructed for both a prototype helmet design, and three traditional helmet designs. The half-face helmet re-sulted in the greatest headform acceleration. the results suggest that the pro-posed open-face helmet design with ventilation slots provides a prom-ising solution for ensuring both user protection and user com-fort in warm climates.
    Source: Networked Digital Library of Theses and Dissertations
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  • 10
    Language: English
    In: Macromolecules, 10/1998, Vol.31(21), pp.7298-7311
    ISSN: 0024-9297
    E-ISSN: 1520-5835
    Source: American Chemical Society (via CrossRef)
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