While shedding light on green space propulsion, the development of non-toxic hypergolic bipropellants has provided alternatives to the conventional, highly toxic propellants. Non-toxic energetic ...hydrocarbon fuels promoted by sodium borohydride were produced, and their hypergolicity with rocket grade hydrogen peroxide was confirmed. Ignition delays ranged from 4 ms to 17 ms, depending on the oxidizer concentration. A 500 N scale thruster utilizing a non-toxic hypergolic bipropellant combination was also developed. With an oxidizer-to-fuel ratio of 5.48, the injector was designed with pentad unlike-impinging jets, one fuel jet orifice and four oxidizer jet orifices for enhancing the mix and atomization of the hypergolic propellants. The operation test was performed, and burning time was established to be 3.5 s. For the demonstrator, the rising time was approximately 158 ms, and the pressure oscillation inside the combustion chamber was approximately ±7.69%. These results indicate the feasibility of this novel concept engine for future space missions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The simulation of the CMS detector operating at the CERN Large Hadron Collider (LHC) is based on the GEANT 4 software package. An alternative simulation of the CMS electromagnetic (ECAL) and hadronic ...(HCAL) central and forward calorimeters based on the GFlash parameterization package has been implemented into the CMS software structure. The GFlash program is a fast simulation of electromagnetic and hadronic showers using parameterizations of longitudinal and lateral shower profiles. We report on tuning the CMS calorimeter response to ECAL and HCAL test-beam data and compare the gain in CPU time to the standard GEANT 4 calorimeter simulation.
Epoxy and its composites have been extensively applied in widespread applications, such as encapsulation of electronics, automobile parts, aircraft components, and so on. The stiffening and ...toughening of epoxy via the incorporation of nanofillers, such as halloysite nanotubes (HNTs), a naturally occurring and low-cost aluminosilicate, have attracted increasing research attention. Herein, we introduce an effective and facile method that substantially enhances the interface of hydroxylated HNTs (h-HNTs) and epoxy matrix by the introduction of urea molecules. As confirmed by the characterization results, urea formed hydrogen bonds with the external surface of the h-HNTs and covalent bonds with the epoxy matrix. The resultant epoxy/h-HNT-urea nanocomposites exhibited significant enhancements simultaneously in tensile strength, Young's modulus, and fracture toughness by 23.4%, 31.4%, and 61.4%, respectively, as compared with the neat epoxy. Through systematic investigation, it was determined that micro-cracking, nanotube bridging, and crack pinning were responsible for the toughening of the epoxy/h-HNT-urea nanocomposites.
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•Improving mechanical properties of epoxy nanocomposite via incorporating hydroxylated halloysite nanotubes/urea hybrids.•Achieving strong interfacial adhesion between epoxy and hydroxylated halloysite nanotubes/urea hybrids.•Simultaneously enhancing tensile strength, Young's modulus, and fracture toughness of epoxy nanocomposite.•Micro-cracking, nanotube bridging, and crack pinning collectively acting as toughening mechanism for epoxy nanocomposite.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Preheating characteristics of hydrogen peroxide monopropellant thruster with manganese oxide catalyst were investigated. Monopropellant thruster requires to preheat a catalyst bed for efficient ...operation in space environment. Optimum preheating temperature of hydrazine monopropellant thruster was well studied. However, preheating characteristics of 90 wt% hydrogen peroxide monopropellant thruster with manganese oxide catalyst are still a subject to research. For this purpose, a 50 N vacuum thrust class monopropellant thruster was employed. The preheating temperature was from 50 °C to 250 °C in increments of 50 °C, and a test in cold start was included as a control group. Their preheating characteristics were expressed in terms of rising time and pressure instability. The results indicate that a significant improvement in rising time and pressure instability was observed until the preheating temperature reached 150 °C. However, in further preheating temperature, the results showed no noteworthy improvements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•A PIRT process is performed for an open-tank-in-pool research reactor.•The process includes the most commonly postulated events of research reactors.•The process is intended to extend the SPACE ...applicability to the research reactors.•A preliminary data set for V&V are proposed for code assessment.•Proposal on further research is given to increase knowledge levels of the RRs.
The benefits of research reactor technology are always essentially accompanied by nuclear safety, which is ensured by a series of supporting analysis such as safety analysis. In order to extend the applicability of the Safety and Performance Analyzing Code (SPACE code) to safety analysis of typical open-tank-in-pool type research reactors using plate-type fuels, a Phenomena Identification and Ranking process was performed for most of the relevant internal event scenarios of a reference research reactor, i.e., the KiJang Research Reactor, designed and under development by the Korea Atomic Energy Research Institute (KAERI). The Structures, Systems, and Components (SSCs) important to nuclear safety of the reactor were included in the PIR processes. A summary of important results from the PIRT study on the research reactors is presented with a proposal on a preliminary set of data bases for a validation and verification matrix in addition to research issues.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
With the emergence of large-language models (LLM) and generative AI, which require an enormous amount of model parameters, the required memory bandwidth and capacity for high-end systems is on an ...unprecedented increase. To meet this need, we present an extended version of the high-bandwidth memory-3 (HBM3 DRAM), HBM3E, which achieves a 1280GB/s bandwidth with a cube density of 48GB. New design schemes and features, such as all-around power-through-silicon via (TSV), a 6-phase read-data-strobe (RDQS) scheme, a byte-mapping swap scheme, and a voltage-drift compensator for write data strobe (WDQS), are implemented to achieve extended bandwidth and capacity with enhanced reliability. The overall architecture and specifications, such as bump map footprint, the number of channel and I/Os, and the operation voltage, are identical to the latest HBM3 1, 2; therefore, backward compatibility is provided, avoiding system modification.
We show that driving speed profiles with high spatial resolution can be constructed using large samples of GPS data collected from vehicle fleets, consumer navigation devices, and smart phones. Such ...historical speed profiles are expected to help adaptive cruise control systems or autonomous vehicles navigate in a manner consistent with the way people drive. Knowing in advance the speed profiles of a trip may help the development of more energy efficient systems.
This thesis presents the search for neutral Minimal Supersymmetric extension of Standard Model(MSSM) Higgs bosons decaying to tau pairs where one of the taus decays leptonically, and the other one ...hadronically. CDF Run II data with special characters omittedint = 310 pb-1 are used. There is no evidence of MSSM Higgs existance, which results in the upper limits on σ(pp¯ → ) × BR( → ττ) in mA range between 115 and 250 GeV. These limits exclude some area in tan β vs. mA parameter space.
We analyzed reports for 59,073 contacts of 5,706 coronavirus disease (COVID-19) index patients reported in South Korea during January 20-March 27, 2020. Of 10,592 household contacts, 11.8% had ...COVID-19. Of 48,481 nonhousehold contacts, 1.9% had COVID-19. Use of personal protective measures and social distancing reduces the likelihood of transmission.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The aim of this study was to evaluate the relation among the quality and freshness traits of chicken breast meat during storage for 12 d at 4°C. In addition, correlations between freshness ...traits and torrymeter values were examined. The L* and a* value of the color was constant; however, the b* value increased on day 5 of storage (P < 0.05). The shear force value significantly decreased, whereas the 2-thiobarbituric acid reactive substances value significantly increased during storage. Regarding the sensory properties, the off-odor and the drip loss increased along with the decrease in color and overall acceptability evaluated by the panelist. The pH, total microorganism counts, and volatile basic nitrogen (VBN) value of chicken breast significantly increased following storage, whereas the torrymeter value and overall acceptability of chicken breast meat significantly decreased from 12.80 to 4.53 and from 6.14 to 1.86, respectively. The VBN value was positively correlated with the pH and total microorganism counts, and the pH value was positively correlated with the total microorganism counts. The torrymeter value was associated with the VBN (−0.918, P < 0.01), pH (−0.973, P < 0.001), total microorganism counts (−0.975, P < 0.001), and overall acceptability (0.884, P < 0.01). These results suggest that the tested traits highly correlate with torrymeter value and it can be used as an indicator of freshness of chicken meat.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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