Search

This study presents a novel manufacturing method of large-scale, soft magnetic FeSi samples (Si 3.5 wt%) with enhanced magnetic properties, devoid of defects, through the application of direct energy deposition (DED). The effects of different manufacturing process parameters on grain morphology (i.e., size, direction, texture) were systematically investigated. A large volume ratio (68.3%) of Goss texture ({110} < 001 >) was formed at the as-printed stage with the grain direction of ~ 33° toward the building direction. The volume ratio of Goss texture was increased to 82.7% after post-heat treatment at 1050 °C for 2 h. The maximum relative permeability of 10710 was achieved after post-heat treatment at 1050 °C for 2 h, which is comparable to commercially available FeSi steel made by the traditional manufacturing method. The magnetic performance results indicate potential improvement of magnetic properties with further optimized grain structure and elevated post-heat treatment temperature. DED-printed FeSi showed higher microhardness and yield strength (284 HV and 625 MPa) compared to FeSi from conventional manufacturing methods. [ABSTRACT FROM AUTHOR]

This paper analyzes a scenario in which two bidders compete for two objects sold at two second-price auctions. Each bidder's valuations of the two objects are affiliated, and participating in each auction is costly. Bidders make their participation decisions for the two auctions sequentially, in that they decide whether to enter the second auction after observing their entry decisions for the first auction. After making their participation decisions for the two auctions, bidders choose their bids in any auction they participate in. We derive the properties of equilibria and provide a sufficient condition for their existence. Due to affiliation and the presence of participation costs, a bidder's entry into the first auction signals his strong interest in the object sold at the second auction. Hence, a bidder with a higher valuation of the second object is more likely to participate in the first auction in order to deter his opponent from entering the second auction. We then compare the models of sequential and simultaneous participation decisions in terms of equilibrium cutoffs and the equilibrium probability of entry into the two auctions. Lastly, we discuss the effects of the order of entry decisions on the revenues in the two auctions as well as the total revenue. [ABSTRACT FROM AUTHOR]

In general, a leaner mixture condition improves combustion efficiency in compression ignition (CI) combustion using diesel. However, in the case of leaner air–fuel mixture conditions, it disturbs flame propagation in spark ignition combustion using gasoline, i.e., low reactivity fuel, causing a decrease in combustion efficiency. Since dual-fuel combustion in a CI engine typically involves the use of high- and low-reactivity fuels together, the differing reactivity conditions in the cylinder become as important as the local equivalence ratio in the cylinder. Thus, there is a need to verify the effect of a leaner mixture condition on combustion efficiency in dual-fuel CI combustion. For this reason, this study experimentally evaluates the effects of varying equivalence ratios on the combustion efficiency of gasoline/diesel dual-fueled CI combustion in a 0.4-L single-cylinder engine under low-speed (1500 rpm) and low-load (total LHV 570 J/str) conditions. To vary the equivalence ratios, intake pressures and exhaust gas recirculation (EGR) rates were, respectively, changed under the part-load condition. The results emphasize that as the equivalence ratio becomes leaner by increasing the intake pressure, combustion efficiency worsens due to the low reactivity properties and certain flame propagation modes of gasoline combustion. On the contrary, increasing the EGR rate did not significantly influence combustion efficiency, but it effectively helped reduce nitrogen oxide (NOx) emissions. Based on these results, it is concluded that optimizing dual-fuel CI combustion to suppress NOx emissions is better achieved using EGR, rather than creating a leaner mixture condition. [ABSTRACT FROM AUTHOR]

In this experiment, it was experimentally investigated the combustion and exhaust characteristics, as well as the thermal efficiency, of RCCI combustion using gasoline, ethanol, and propane as low-reactivity fuels under four operating conditions. For each operating condition, gISNOx was limited to 0.15 g/kWh, and gISSmoke was limited to below 15 mg/kWh. The experiment was conducted by determining the operating conditions that satisfied these limitations and resulted in the highest city thermal efficiency. The low-reactivity fuels were supplied by port injection, while diesel was directly injected into the combustion chamber using a diesel injector. As a result, when gasoline is replaced with low-carbon fuels like ethanol and propane, the reduction in CO2 emissions occurred. Under maximum power conditions, using ethanol allowed for a maximum reduction in CO2 emissions of 6.81%. Depending on the driving conditions, ethanol showed a reduction ranging from 3.60 to 6.81%, while propane exhibited a reduction ranging from 3.10 to 5.64%. Additionally, by substituting with ethanol and propane, the GIE could be improved up to 44.73 and 43.56%, respectively. [ABSTRACT FROM AUTHOR]

This study aimed to design energy-efficient systems for reactive distillation to simultaneously produce methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) from mixed feeds of methanol and ethanol. In this work, two new designs are proposed. One is the individual production of each ether, involving two reactive distillation columns after feed alcohol separation, while the other for the co-production of both ethers in a single reactive distillation column without the alcohol separation. Rigorous simulations of the two proposed systems were conducted with varying ratios of the two alcohols in actual process streams. When the methanol feeding was dominant, the co-production system exhibited better performance than the individual ether production system. This was due to the lower temperatures inside the alcohol separation column, resulting in a lower relative volatility of methanol and increasing the heat duty in the alcohol separation column. However, when the amount of ethanol was higher than that of methanol, the individual production system outperformed the co-production system. This was attributed to the unfavorable reaction equilibrium of ETBE production, leading to a high internal flowrate in the co-production reactive distillation column. The external heat integration of each design can bring further reduction in energy consumption and CO2 emissions, but the results follow the same dependence on the feed alcohol ratio. [ABSTRACT FROM AUTHOR]

In this study, the effects of varying excess air ratios on a 2.0 L naturally aspirated (NA) hydrogen-fueled spark ignition (SI) engine were evaluated under low-load conditions by using port fuel injection (PFI) and direct injection (DI) systems. The engine speeds chosen were 1,200 rpm and 2,000 rpm. The excess air ratio was varied between 1.0 and 2.7 by controlling the throttle and hydrogen fuel rate under a brake mean effective pressure of 0.4 MPa. The combustion mechanism, net indicated thermal efficiency (ITE), brake thermal efficiency (BTE), gas exchange efficiency, mechanical efficiency, and engine-out nitrogen oxide (NOx) emissions were mainly discussed. The results indicated that the main combustion duration of PFI was shorter than that of DI due to its homogeneity, and the ITE values of PFI were similar or slightly lower than those of DI. However, as the mechanical efficiency of DI was higher than that of PFI, the BTE values of DI were always higher than those of PFI (the maximum BTE was 39.7 %). The NOx reduction potential of DI was superior to that of PFI due to stratified combustion, and its lowest value was 0.03 g/kWh. In addition, as the CO2 concentration in the exhaust gas increased, the brake-specific CO2 reduced (< 5.71 g/kWh). [ABSTRACT FROM AUTHOR]

Hydrogen is advantageous for use in internal combustion engines (ICEs) because of its high laminar flame speed and carbon-neutral characteristics. However, because of its low minimum ignition energy, abnormal combustions such as back-fire, pre-ignition, and knocking hinder its efficient supply as a fuel to ICEs under near stoichiometric conditions. Hence, in this study, the effect of various excessive air ratios (λ) on the performance of a hydrogen-fueled spark ignition engine using port fuel injection (PFI) was evaluated under wide-open throttle conditions. After determining the highest limit for the maximum brake torque, a hydrogen direct injection (DI) system was applied under the same λ and abnormal combustion limits to improve the brake power (BP). Results show that at 1,500 rpm, a maximum BP of 14.7 kW was achieved under a λ value of 1.4 with PFI; however, it can be increased up to 21.1 kW using DI with the same brake thermal efficiency under a compression ratio of 14. [ABSTRACT FROM AUTHOR]

Dual-fueled combustion, using high and low reactivity fuels simultaneously, is a promising combustion method that enables reduction of nitrogen oxides (NOx) emission. However, the total amount of NOx emissions in the exhaust gas is strongly influenced by the overall excessive air ratio (lambda) of air—fuel mixture. Thus, lean mixture condition is important for NOx emissions although RCCI operating condition is applied. In addition, not only reduction of emissions, but improvement in BTE requires the boost pressure to be increased. Thus, variations in boost pressure via a controlling turbocharger system was evaluated under general dual-fueled combustion and RCCI conditions using diesel and natural gas fuels while tracing emissions and BTE. The results indicated that higher boost pressure was more effective on RCCI condition in reducing NOx emissions and enhancing BTE and turbocharging system efficiency with lower carbon dioxides, compared to those of general dual-fueled combustion condition. Especially, turbocharger efficiency of dual-fueled combustion was higher than that of diesel single-fueled combustion related with composition of exhaust gas and exhaust gas temperatures. [ABSTRACT FROM AUTHOR]

In this study, a high-load expansion strategy was investigated by varying the effective compression ratio (CR) using the variable valve duration (VVD) method during combustion in a gasoline/diesel dual-fuel premixed compression ignition engine. The effective CR was varied from 15.0 to 10.6 via the retardation of the intake valve closing timing (IVC) at 1,500 rpm. With respect to optimization, the diesel injection timing, fuel ratio, and exhaust gas recirculation (EGR) rate were adjusted for each optimized condition. The limitations were the maximum pressure rise rate (below 10 bar/deg) and in-cylinder pressure (below 150 bar) with NOx < 40 ppm and soot < 0.2 FSN. The results emphasized that when the effective CR was 12.7, the maximum load increased by 10.5 % (gIMEP from 13.3 to 14.7 bar) compared with that at a CR of 15.0. Although the decrease in CR resulted in a gross thermal efficiency loss, the difference was negligible (from 45.9 to 45.5 %). The main reason for high-load expansion was the increase in intake air volume under the same intake pressure upon lowering the CR and the margin for the maximum in-cylinder pressure. From this result, it can be concluded that the Miller cycle is useful for the expansion of high load ranges in premixed combustion systems. [ABSTRACT FROM AUTHOR]

In-cylinder flow motion is important for enhancing combustion in internal combustion engines. There are two major flow motions: tumble and swirl. Tumble enhances the flame propagation speed to spread throughout the entire cylinder. Swirl affects the behavior of diesel spray; an enhanced swirl ratio has been widely used in conventional diesel engines. Because dual-fueled combustion has the characteristics of premixed combustion from background fuels and mixing-controlled combustion from directly injected fuels such as diesel, understanding the effect of in-cylinder flow motion on combustion characteristics in dual-fuel combustion is critical. In this research, the effect of swirl in gasoline and diesel dual-fuel combustion was evaluated with different diesel injection timing conditions. As the dual-fuel combustion engine used in this research was driven by diesel spray, swirl was selected as the main flow motion rather than tumble. The effect of swirl with different diesel injection timings was investigated under low-speed and low-load conditions. The results demonstrate that increasing swirl intensity provokes fast-burning caused by the enhanced air-fuel mixture, decreasing the diesel fraction and allowing more exhaust gas recirculation (EGR) to be used for the reduction of engine-out nitrogen oxides (NOx) and smoke emissions, without reducing thermal efficiency. [ABSTRACT FROM AUTHOR]

We recently reported a lack of interference between inactivated rotavirus vaccine (IRV) and inactivated poliovirus vaccine (IPV) and their potential dose sparing when the two vaccines were administered intramuscularly either in combination or standalone in rats and guinea pigs. In the present study, we optimized the formulations of both vaccines and investigated the feasibility of manufacturing a combined IRV-IPV dissolving microneedle patch (dMNP), assessing its compatibility and immunogenicity in rats. Our results showed that IRV delivered by dMNP alone or in combination with IPV induced similar levels of RV-specific IgG and neutralizing antibody. Likewise, IPV delivered by dMNP alone or in combination with IRV induced comparable levels of neutralizing antibody of poliovirus types 1, 2, and 3. We further demonstrated high stability of IRV-dMNP at 5, 25, and 40 °C and IPV-dMNP at 5 and 25 °C, and found that three doses of IRV or IPV when co-administered at a quarter dose was as potent as a full target dose in inducing neutralizing antibodies against corresponding rotavirus or poliovirus. We conclude that IRV-IPV dMNP did not interfere with each other in triggering an immunologic response and were highly immunogenic in rats. Our findings support the further development of this innovative approach to deliver a novel combination vaccine against rotavirus and poliovirus in children throughout the world. [ABSTRACT FROM AUTHOR]

The effects of intake pressures and EGR rates on the natural gas/diesel dual-fuel combustion under a high load condition (brake power of 100 kW) were evaluated using a 6-L CI engine in this study. Natural gas fraction was fixed as 80% of total input energy for all the dual-fuel combustion operations and engine rotation speed was set to 1,800 rpm. Intake pressure was varied from 0.15 to 0.21 MPa by controlling the waste gate type turbocharger system. EGR rate was changed mainly by controlling EGR valve opening from fully closing to mid-opening to fully opening, but it was also affected when intake pressures were varied. In addition to these intake mixture parameters, diesel injection timing was adjusted in two cases—early and late injections and all the experimental results were compared to those of the neat diesel combustion cases. The results emphasized that the dual-fuel combustion was more sensitive to overall equivalence ratio determined by intake pressures and EGR rates than the neat diesel combustion because it had flame propagation process of premixed natural gas and air mixture. Thus, during the dual-fuel operations, in-cylinder temperature and brake thermal efficiency were decreased as intake pressure was increased. [ABSTRACT FROM AUTHOR]

In this research, it was investigated the energy fraction and emission characteristics of natural gas/diesel dual-fuel combustion in terms of the combustion index such as combustion duration and mass fraction burned 50% (MFB50) of a 6-L heavy-duty compression ignition (CI) engine. The reactivity gradient was varied by changing the diesel injection timing and natural gas energy fraction from 60 to 90%. Engine speed was fixed at 1,200 rpm, and the total input energy from the two fuels was maintained at 11,880 J/cycle for all six cylinders. Diesel injection timing was varied from top dead center (TDC) to 40° before TDC (BTDC) (at intervals of 10°). First, the combustion parameters were analyzed in terms of differences in reactivity gradients. The main combustion parameters considered included ignition delay, combustion duration, and MFB 50. For all cases, the indicated thermal efficiency (ITE) was analyzed with respect to the energy fractions of combustion loss, heat transfer loss, and exhaust loss, to determine the main influences on combustion duration and the MFB 50. Engine-out emission was introduced as an operating parameter associated with ITE and the various losses. These values were compared to those of neat diesel combustion conditions. [ABSTRACT FROM AUTHOR]

We have measured the half-lives of 87mY and 87gY produced from the 89Y(γ, 2n) and 89Y(n, 3n) reactions with the bremsstrahlung end-point energy of 65 MeV and the average neutron energy of 37.2 MeV using an activation and an off-line γ-ray spectrometric technique, respectively. The bremsstrahlung photon was produced by using the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL), whereas the fast neutron was produced from the 9Be(p, n) reaction by using the 45 MeV proton of the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). We have also measured the half-lives of 194Au and 196m2,gAu produced from the 197Au(γ, xn; x = 1, 3) and 197Au(n, xn; x = 2, 4) reactions with the bremsstrahlung end-point energy of 60 MeV and the average neutron energy of 37.2 MeV using the same technique and the same facilities as mentioned above. The induced γ-ray activities of the irradiated samples were measured by using an energy- and efficiency calibrated high purity germanium (HPGe) detector. The spectrum analysis has been done by using the ROOT software to separate signals from background. The measured half-lives are compared with the literature values and are in general agreement with each other within the uncertainties. [ABSTRACT FROM AUTHOR]

In this research, the effects of three operating parameters (Diesel injection timing, propane ratio, and exhaust gas recirculation (EGR) rates) in a diesel-propane dual fuel combustion were investigated. The characteristics of dual-fuel combustion were analyzed by engine parameters, such as emission levels (Nitrogen oxides (NO) and particulate matter (PM)), gross indicated thermal efficiency (GIE) and gross IMEP Coefficient of Variance (CoV). Based on the results, improving operating strategies of the four main operating points were conducted for dual-fuel PCCI combustion with restrictions on the emissions and the maximum pressure rise rate. The NOx emission was restricted to below 0.21 g/kWh in terms of the indicated specific NO (ISNO), PM was restricted to under 0.2 FSN, and the maximum pressure rise rate (MPRR) was restricted to 10 bar/deg. Dual-fuel PCI combustion can be available with low NO, PM emission and the maximum pressure rise rate in relatively low load condition. However, exceeding of PM and MPRR regulation was occurred in high load condition, therefore, design of optimal piston shape for early diesel injection and modification of hardware optimizing for dual-fuel combustion should be taken into consideration. [ABSTRACT FROM AUTHOR]

Environmental problems have become a major issue for diesel engine development. Although emission aftertreatment systems such as DPFs (diesel particulate filters), LNTs (lean NOx traps) and SCR (selective catalytic reduction) have been used in diesel vehicles, the manufacturing cost increase caused by this equipment can be hard to be control. Thus, it is better for engine emissions to be reduced by improving the combustion system. A dual-fuel combustion concept is a recommended method to improve a combustion system and effectively reduce emissions. Low reactivity fuel including gasoline and natural gas, which was supplied to the intake port by the FPI (port fuel injector), improved the premixed air-fuel mixture conditions before ignition. Additionally, a small amount of high reactivity fuel, in this case diesel, was injected into the cylinder directly as an ignition source. This dual-fuel combustion promises lower levels of NOx (nitrogen oxide) and PM (particulate matter) emissions due to the elimination of local rich regions in the cylinder. However, it is challenging to control the dual-fuel combustion because the combustion stability and efficiency deteriorate due to the lack of ignition source and reactivity. Thus, it is important to establish an appropriate dual-fuel operating strategy to achieve stable, high efficiency and low emission operation. As a result of this research, a detailed operating method of dual-fuel PCI (premixed compression ignition) was introduced in detail at a low speed and low load condition by using a single cylinder diesel engine. Engine operating parameters including the gasoline ratio, a diesel injection strategy consisting of multiple injectors and timing, the EGR (exhaust gas recirculation) rate and the intake pressure were controlled to satisfy the low ISNOx (indicated specific NOx) and PM emissions levels (0.21 g/kWh and 0.1 FSN, 0.040 g/kWh, respectively) as per the EURO-6 regulation without any after-treatment systems. The results emphasized that a well-constructed dual-fuel PCI operating strategy showed low NOx and PM emissions and high GIE (gross indicated fuel conversion efficiency) with excellent combustion stability. [ABSTRACT FROM AUTHOR]

The objective of this study is to suggest a methodology for estimating the time-variant probable maximum precipitation. First, the greatest amount of precipitation for a relatively long duration, e.g., a month or longer, defined as the Long-term Probable Maximum Precipitation (LPMP) in the present work was estimated. Then, the procedure for using the LPMP estimates for determining the temporally varied upper limit of precipitation during a certain period of the year, defined as the time-variant PMP (TPMP) in this study was implemented. Hershfield's statistical approach was used to estimate LPMP, i.e., monthly, calendar monthly, and cumulative monthly, for each of 61 weather stations located in South Korea, and nationwide distribution maps of three types of LPMP were made. In particular, using the cumulative monthly PMP estimates and total antecedent precipitation prior to a certain time, the TPMP for a certain duration was forecast for example problems. From the case study for precipitation data at Chungju weather station, TPMP forecasts at certain stormy periods were substantially smaller than the design PMP, which implies that reservoir operation for flood control based on the design PMP may be too restrictive for some period. It is expected that the TPMP can serve as a complementary index to increase the water supply of a reservoir. [ABSTRACT FROM AUTHOR]

Chromospheric activities before solar flares provide important clues to the mechanisms that initiate solar flares, but are as yet poorly understood. We report a significant and rapid H $\upalpha$ line broadening before the solar flare SOL2011-09-29T18:08 that was detected using the unprecedented high-resolution H $\upalpha$ imaging spectroscopy with the Fast Imaging Solar Spectrograph (FISS) installed on the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The strong H $\upalpha$ broadening extends as a blue excursion up to −4.5 Å and as a red excursion up to 2.0 Å, which implies a mixture of velocities in the range of $-130~\mbox{km}\,\mbox{s}^{-1}$ to 38 km s derived by applying the cloud model, comparable to the highest chromospheric motions reported before. The H $\upalpha$ blueshifted broadening lasts for about six minutes and is temporally and spatially correlated with the start of a rising filament, which is later associated with the main phase of the flare as detected by the Atmosphere Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The potential importance of this H $\upalpha$ blueshifted broadening as a preflare chromospheric activity is briefly discussed within the context of the two-step eruption model. [ABSTRACT FROM AUTHOR]

Using comparative data, this article examines the level and distribution of participation in adult education (AE) opportunities among countries that participated in PIAAC (Programme for the International Assessment of Adult Competencies). It considers observed cross-country patterns in relation to some mechanisms that drive unequal chances to participate and to some policy issues that surround the provision, governance, and financing of different types of adult learning. It also explores recent policy developments relevant to AE in three selected countries (Korea, Norway, and Vietnam). [ABSTRACT FROM AUTHOR]

In Korea, few investigations from the waste incineration were conducted on greenhouse gas emitted. This research calculates and compares non-CO concentrations and emission factors for the facilities of an incinerator comprising a pyrolysis melting incineration type (incinerator A) and a stoker incineration type (incinerator B). An analysis was made of daily average concentrations of the samples collected over a 24-h period, and the results show that incinerator A had a CH concentration of about 1.9 ppm and a NO concentration of about 1.2 ppm; incinerator B had a CH concentration of about 2.1 ppm and a NO concentration of about 4.5 ppm. A pyrolysis melting incineration type showed a similar value to the emission factor derived from a gasification melting furnace suggested by NIR in Japan, and there is about a 5.1 times difference between the pyrolysis melting incineration type and the stoker incineration type used in this study. This implies that, when the same default emission factor is applied without giving consideration to the characteristics of each incinerator, greenhouse gas emissions may be excessively calculated. [ABSTRACT FROM AUTHOR]

While the Intergovernmental Panel on Climate Change classifies coal as anthracite, bituminous coal, and sub-bituminous coal, Korea only distinguishes coal as anthracite and bituminous coal while sub-bituminous coal is considered bituminous coal. As a result, Korea conducted research in the CO emission factors of anthracite and bituminous coal, but largely ignored sub-bituminous coal. Therefore, the purpose of this research is to develop the CO emission factor of sub-bituminous coal by classifying sub-bituminous coal from resources of bituminous coal activities collected in Korea between 2007 and 2011. The 2007-2011 average carbon content of sub-bituminous coal was analyzed to be 69.63 ± 3.11 %, the average hydrogen content 4.97 ± 0.37 %, the inherent moisture 12.60 ± 4.33 %, the total moisture 21.91 ± 5.45 %, and the dry-based gross calorific value was analyzed to be 5,914 ± 391 kcal/kg; using these analyzed values, the as-received net calorific value was found to be 20.75 ± 7.59 TJ/Gg and the CO emission factor was found to be 96,241 ± 4,064 kg/TJ. In addition, the 62.7 million ton amount for the 2009 greenhouse gas emission from sub-bituminous coal as estimated with the analyzed value of this study is an amount that is equivalent to 11.1 % of the 2009 total greenhouse gas emission amount of 564.7 million tons, and this amount is larger than the 9.3 % for the industrial processes sector, 3.3 % for the agricultural sector and 2.5 % for the waste sector. Therefore, it is important to reflect the realities of Korea when estimating the greenhouse gas emission from such sub-bituminous coals. [ABSTRACT FROM AUTHOR]

Consumption of primary energy in Korea increased 5.25 % per year over a 10 years span starting in 1990. Korea ranked 8th in primary energy consumption in 2011; coal consumption increased 35 % from 87,827 million tons in 2006-119,321 tons in 2010. Heavy energy-consuming countries consistently conduct research to develop an emission factor of Tier 2 level, reflecting the characteristics of the fuel that they use. To calculate the emission factor of bituminous coal for fuel, this study developed emission factor and calculated emission amount by implementing fuel analysis on bituminous coal consumed in Korea between 2007 and 2009. CO emission factor calculated by fuel analysis method is 95,315 kg/TJ, which is 0.75 % higher than the default value suggested by IPCC. The emission amount calculated by using the CO emission factor in this study is 231.881 million tons, which has a difference of 1.739 million tons compared to the IPCC default value. [ABSTRACT FROM AUTHOR]

To draw a comparison of the effect of multiple injection strategy on the engine-out emissions under two different EGR rate conditions, the effect of pilot injection on emissions and combustion was evaluated and discussed in part 1. Thus, in the second research as part 2, the effects of post injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30 % and 60 %). Since the behavior of diesel combustion is significantly different as EGR rate is changed, the characteristics of post injection was different between two EGR rate conditions. This research was investigated as varying injection parameters such as the timing and quantity of the post injection. The results show that the close post injection with injection interval as 10 degree has the potential to reduce PM emission, regardless of EGR rate. However, the reason of reduction of PM emission is different for each case. For a moderate EGR rate condition, close post injection with interval 10 degree enhances the fuel at bottom of bowl. Thus, the distribution of fuel can be improved. On the other hand, for a heavy EGR rate condition, close post injection with interval 10 degree has the charge cooling effect to prolong the ignition delay, rather than well-matched injection targeting. Especially, there is an effect to oxidize PM emission under moderate EGR rate condition as post injection is applied. However, post injection for late cycle of combustion under heavy EGR rate condition does not oxidize PM emission due to low oxygen concentration (∼ 10%). [ABSTRACT FROM AUTHOR]

Many countries are now creating world-class universities (WCUs) as essential parts of their higher education reform agendas, and as national goals. It is legitimate to ask whether every county that aspires to build a WCU can do so-especially developing countries. To answer this question, this paper provides a three-step framework. The first step in building a WCU is to understand its characteristics. The second is for the country to systematically assess whether it has the capacity to create a WCU by rationally appreciating the challenges it would face in creating one. Third, it must understand, given the challenges discovered in the second step, what to do to create a WCU. Considering this framework, only a few developing countries have the potential to foster a WCU. Thus it is difficult for many universities in developing countries to enter an existing market already occupied by well-developed education systems and universities. [ABSTRACT FROM AUTHOR]

As vehicle emissions regulations have become stricter, improving injection strategies and using high EGR rates has become important to reduce engine-out emissions. Previous research has found that, a multiple injection strategy with a pilot or post injection has the potential to improve the distribution of the air-fuel mixture or oxidation. Thus, it is important to determine the effect of multiple injection strategies on the engine-out emissions. Especially, since the latest diesel engines have used high EGR rates to reduce NO emission, the target of emissions is different from that of moderate EGR rate condition. Under heavy EGR rate condition, it is needed to improve combustion efficiency by reduction of CO and THC emissions. Therefore, in the first research as part 1, the effects of pilot injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30% and 60%). The characteristics of the pilot injection were different between the two EGR rate conditions because the behavior of diesel combustion is significantly different when the EGR rate is changed. This research condition was investigated using varying injection parameters such as the timing and quantity of the pilot injection. The results show that each different pilot injection strategy was suggested between two EGR rate conditions to reduce engine-out emissions. Under moderate EGR rate condition, very earlier pilot SOI with large amount has the potential to reduce NO and PM emissions simultaneously. On the other hand, under heavy EGR rate condition, the closest pilot SOI to main SOI has the potential to reduce CO and THC emissions. [ABSTRACT FROM AUTHOR]

In this research, in order to develop technology/country-specific emission factors of methane (CH) and nitrous oxide (NO), a total of 585 samples from eight gas-fired turbine combined cycle (GTCC) power plants were measured and analyzed. The research found that the emission factor for CH stood at '0.82 kg/TJ', which was an 18 % lower than the emission factor for liquefied natural gas (LNG) GTCC '1 kg/TJ' presented by Intergovernmental Panel on Climate Change (IPCC). The result was 8 % up when compared with the emission factor of Japan which stands at '0.75 kg/TJ'. The emission factor for NO was '0.65 kg/TJ', which is significantly lower than '3 kg/TJ' of the emission factor for LNG GTCC presented by IPCC, but over six times higher than the default NO emission factor of LNG. The evaluation of uncertainty was conducted based on the estimated non-CO emission factors, and the ranges of uncertainty for CH and NO were between −12.96 and +13.89 %, and −11.43 and +12.86 %, respectively, which is significantly lower than uncertainties presented by IPCC. These differences proved that non-CO emissions can change depending on combustion technologies; therefore, it is vital to establish country/technology-specific emission factors. [ABSTRACT FROM AUTHOR]

Introduction: Korea has been making efforts to reduce greenhouse gas (GHG) emissions, including a voluntary commitment to the target of a 30% reduction, based on business-as-usual of the total GHG emission volume, by 2020; 2006 IPCC Guidelines provided default values, applying country-specific emission factors was recommended when estimating national greenhouse gas emissions. Results and discussion: This study focused on anthracite produced in Korea in order to provide basic data for developing country-specific emission factor. This study has estimated CO emission factors to use worksheet of which five steps consisted according to the fuel analysis method. Conclusion: As a result, the average of net colorific value for 3 years (2007∼2009) was 4,519 kcal/kg, and the CO emission factor was calculated to be 111,446 kg/TJ, which is about 11.8% lower than the 2006 IPCC guidelines default value, and about 7.9% higher than the US EPA emission factor. [ABSTRACT FROM AUTHOR]

As EURO-6 regulations will be enforced in 2014, simultaneous reduction of NO and PM emissions becomes an important issue in recent diesel engine research. New combustion concepts, such as LTDC and pHCCI, have been introduced to overcome the NO and PM trade-off relation. However, these novel combustion concepts are usually implemented with a high EGR rate and by advancing the main injection timing which cause high CO and THC emissions along with poor fuel consumption due to low combustion efficiency. Therefore, the split injection strategy, which was consisted of applying post injection close to the main injection, was carried out in this experiment. Specifically, two different nozzles - a 7-hole conventional nozzle and a 12-hole double-row nozzle - were evaluated to determine the effects of nozzle configurations on engine-out emissions. The result shows that CO emission was reduced by the close post injection strategy regardless of the nozzle configuration. However, THC and PM emissions were reduced only when the 12-hole double-row nozzle was used. Thus, the use of close post injection with the 12-hole double-row nozzle could increase the combustion efficiency in heavy EGR conditions. [ABSTRACT FROM AUTHOR]

In this study, the solid, porous, and hollow polymer microspheres were prepared using a simple and novel production method based on Shirasu porous glass (SPG) membrane emulsification and suspension polymerization. With the SPG membrane, uniform-sized emulsion monomer droplets containing divinyl benzene (DVD), styrene (St), hexadecane (HD), and an initiator were prepared in an aqueous phase using a membrane emulsification technique. The aqueous phase contained hydroquinone (HQ) as a water-soluble inhibitor and polyvinylpyrrolidone (PVP) as a stabilizer. The morphology of the particles was affected by the stabilizer, St/DVB ratio, hexadecane amount, and initiator amount. Through this study, the porous polymer microspheres were achieved when the HD content was 30 wt% relative to the monomer and the hollow polymer microspheres was achieved when the HD content was more than 62.5 wt% relative to the monomer. These results highlight the phase separation speed between polystyrene (PSt) and HD. [ABSTRACT FROM AUTHOR]

Electrically conducting silicone rubber composites were prepared by the incorporation of conducting fillers including carbon black, carbon fiber, and carbon nanotubes. Herein, silicone/multi-walled carbon nanotube (MWNT) composites were produced by mechanical mixing, where glass beads (GBs) were introduced to significantly improve the dispersion of MWNTs in a silicone matrix. The dispersion of MWNTs in a silicone matrix is related to the ball-bearing effect of GBs. The electrical conductivity of the silicone/MWNT/GB composite was approximately two times higher than that of the composite without GBs due to the improved distribution uniformity of MWNTs in the silicone matrix. In addition, the presence of GBs in the silicone matrix improves the mechanical properties, such as the tensile strength and elongation at break as well as the electrical conductivity. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to enhance the thermal conductivity of MWCNT filled poly(dimethyl siloxane) (PDMS) composites, the MWCNT was coated with silica layer by three step reactions. The composites filled with raw and silica-coated MWCNTs were prepared and the properties were investigated in terms of the curing characteristics, mechanical properties, and thermal conductivity. Due to the poor compatibility between raw MWCNT and PDMS, raw MWCNT showed poor dispersion uniformity and wettability in PDMS. On the other hand, due to the chemical affinity between silica/MWCNT and PDMS throughout the hydrogen bonding, the silica-coated MWCNT filled PDMS showed improved mechanical properties in terms of tensile strength and 100% modulus, and good interfacial compatibility than raw MWCNT incorporated PDMS. Finally, the good wettability of silica/MWCNT in PDMS resulted in higher thermal conductivity caused from the facile phonon movement at the interface even with the smaller MWCNT contents. [ABSTRACT FROM AUTHOR]

To carry out miniemulsion polymerization of styrene in the presence of carbon black, carbon black was hydroxylated using potassium permanganate with the aid of a phase transfer catalyst, tetrabutyl ammonium bromide (TBABr). The hydroxylated carbon black was further reacted with oleic acid. The surface modification of carbon black with oleic acid was confirmed by FTIR, XPS, and TEM. The oleic acid-coated carbon black was successfully microencapsulated by polystyrene using miniemulsion polymerization. Polymerization failed when pristine carbon black was used. However, satisfactory conversion (> 96%) was achieved using the oleic acidmodified carbon black. The existence of a polystyrene layer was confirmed by TEM. In contrast the pristine carbon black, the oleic acid-coated carbon black did not act as a radical scavenger during polymerization. [ABSTRACT FROM AUTHOR]

We investigated the feasibility of dispersion polymerization without any stabilizer, which has been considered essential for ensuring colloidal stability. By employing small amounts of a lyophilic comonomer, 4-vinyl pyridine, styrene was successfully polymerized by dispersion polymerization in aqueous alcohol without stabilizer to afford stable poly(styrene- co-4-vinyl pyridine) copolymer microspheres. The stable microspheres were produced in the 4-vinyl pyridine range of 2-15 wt% to styrene. Without 4-vinyl pyridine, severely coagulated particles were obtained, implying that the poly(4-vinyl pyridine) moiety endowed colloidal stability. The polymerization kinetics, behavior, and properties of the ultimate particles showed general features of dispersion polymerization. The study results suggest that stabilizer-free dispersion polymerization is possible, thereby facilitating the synthesis of impurity (stabilizer)-free polymer particles. [ABSTRACT FROM AUTHOR]

Core/shell (±)PS/(−)silica nanocomposite particles were synthesized by dispersion polymerization using an amphoteric initiator, 2,2′-azobis [ N-(2-carboxyethyl)-2,2-methylpropionamidine](HOOC(CH)HN(HN=) C(CH)CN=NC (CH)C(=NH)NH (CH)COOH), VA-057. Negatively charged (−6.9 mV) silica was used as the stabilizer. The effects of silica addition time and silica and initiator concentrations were investigated in terms of polymerization kinetics, ultimate particle morphology, and size/size distribution. Uniform hybrid microspheres with a well-defined, core-shell structure were obtained at the following conditions: silica content = 10−15 wt% to styrene, VA-057 content=above 2 wt% to styrene and silica addition time=0 min after initiation. The delay in silica addition time retarded the polymerization kinetics and broadened the particle size distribution. The rate of polymerization was strongly affected by the silica content: it increased up to 15 wt% silica but then decreased with further increase in silica content. However, the particle size was only marginally influenced by the silica content. The zeta potential of the composite particles slightly decreased with increasing silica content. With increasing VA-057 concentration, the PS microspheres were entirely coated with silica sol above 1.0 wt% initiator. [ABSTRACT FROM AUTHOR]

Solar active region coronae are known for strong magnetic fields permeating tenuous plasma, which makes them an ideal astronomical laboratory for magnetohydrodynamics research. It is, however, relatively less known that this physical condition also permits a very efficient radiation mechanism, gyro-resonant emission, produced by hot electrons gyrating in the coronal magnetic field. As a resonant mechanism, gyro-emission produces high enough opacity to fully reveal the coronal temperature, and is concentrated at a few harmonics of the local gyrofrequency to serve as an excellent indicator of the magnetic field. In addition, the polarization of the ubiquitous free–free emission and a phenomenon of depolarization due to mode coupling extend the magnetic field diagnostic to a wide range of coronal heights. The ability to measure the coronal temperature and magnetic field without the complications that arise in other radiative inversion problems is a particular advantage for the active region radio emissions available only at these wavelengths. This article reviews the efforts to understand these radiative processes, and use them as diagnostic tools to address a number of critical issues involved with active regions. [ABSTRACT FROM AUTHOR]

The surface of rutile titania nanoparticles was chemically modified by reacting with alkoxy silane. The surface and rheological properties in silicone oil having a wide range of viscosity were investigated. Total surface free energy (γ) of the titania particles decreased from 53.12 to 26.94 mJ/m as the silane used for surface treatment was increased from 0 to 5.0 wt%. The surface free energy of neat silane was 25.5 mJ/m which is quite close to that of titania particles treated with 5.0 wt% silane. Due to the hydrophobic nature of treated-titania, the contact angle was accordingly higher for polar solvent in the order of water > ethylene glycol > formamide> α-bromonaphthalene. In sum of rheological behavior, as the applied shear stress or viscosity of the silicone oil increased, the titania particles tend to form layers and agglomerated clusters, showing shear-thinning and shear-thickening behaviors, sequentially. A good dispersion of discrete titania particles obeying a Newtonian flow behavior was achieved at a surface energy or low concentration of silane-treated titania particles in hydrophobic silicone oil. [ABSTRACT FROM AUTHOR]

This paper is a numerical investigation of incident wave interactions with a moored, pontoon-type floating breakwater. We employ a boundary element method to solve the diffraction and radiation boundary value problems describing the situation of a moored floating breakwater in waves. The numerical model includes the hydrodynamic and mooring analyses, verified by the previous numerical and experimental results. Using the numerical model, we are able to assess the hydrodynamic performance of a moored single and dual pontoon floating breakwaters in regular waves. In particular, the effects of the mean wave drift force on the mooring system and wave attenuation characteristics are examined. The numerical results show that mooring tensions are significantly influenced by the mean wave drift force. However, the effect of the drift force on the performance of the floating breakwater in regular waves is not as significant. [ABSTRACT FROM AUTHOR]

The dual-porosity model and the discrete fracture network model are being used for the analysis of groundwater flow in a fractured aquifer. The dual-porosity model assumes that the porous medium consists of two continua at the macroscopic level, namely, fracture and matrix block. Saturated water flow in the matrix as well as in the fracture pore system is described by using two flow equations which are coupled by water transfer term. The discrete fracture network model assumes that only fracture forms paths for seeping water and that the conductivity in matrix block is neglected. The cubic law describing water flow through fractures, yields system of equations at each node. In this paper, it is attempted to investigate the applicability of the dual-porosity model and the discrete fracture network model and to establish a relationship between the dual-porosity approach and the discrete fracture network approach with a view to bridging the gap between two models. [ABSTRACT FROM AUTHOR]

It is well recognized that the phenomenon of depolarization (the conversion of polarized radio emission into unpolarized emission) of microwaves over solar active regions can be used to infer the coronal electron density once the coronal magnetic field is known. In this paper we explore this technique using an active region for which we have excellent radio data showing depolarization at two frequencies, and for which we have an excellent magnetic field model which has been tested against observations. We show that this technique for obtaining coronal densities is very sensitive to a number of factors. When Cohen's (1960) theory where depolarization is due to magnetic field rotation alone is used, the result is particularly sensitive to the location of the surface on which the magnetic field is orthogonal to the line of sight. Depending on whether we take into account the presence of electric currents in the photosphere or not, their extrapolation into the corona can result in very different heights being deduced for the location of the depolarization strip, and this changes the density which is then deduced from the depolarization condition. Such extreme sensitivity to the magnetic field model requires that field extrapolations be able to accurately predict the polarity of magnetic fields up to coronal heights as high as ∼ 105 km in order to exploit depolarization as a density diagnostic. [ABSTRACT FROM AUTHOR]

Microwave emission from solar active regions at frequencies above 4 GHz is dominated by gyroresonance opacity in strong coronal magnetic fields, which allows us to use radio observations to measure coronal magnetic field strengths. In this paper we demonstrate one powerful consequence of this fact: the ability to identify coronal currents from their signatures in microwave images. Specifically, we compare potential-field (i.e., current-free) extrapolations of photospheric magnetic fields with microwave images and are able to identify regions where the potential extrapolation fails to predict the magnetic field strength required to explain the microwave images. Comparison with photospheric vector magnetic field observations indicates that the location inferred for coronal currents agrees with that implied by the presence of vertical currents in the photosphere. The location, over a neutral line exhibiting strong shear, is also apparently associated with strong heating. [ABSTRACT FROM AUTHOR]