895 research outputs found
Pressure Transmission in the Compaction Process for Nickel Powder using Finite Element Methods
The compression process is one of the more widely used industrial manufacturing methods for fabricating desired shape of specimens with various materials such as metals and ceramics. In the compaction process, the upper punch moves into the powder, and force is transmitted between particles, then achieving densification. In this process, the powder can be considered to be in a particulate state, which means that while the powder consists of solids, it has characteristics quite similar to the fluid. Therefore, particles in the process can be seen as responding to hydrostatic pressure, and it can be assumed that the pressure is constant. However, the forces acted on the inter-particle continue to change during the process. Many parameters affect the force change, including compaction speed and the contact angle between particles. However, it is very difficult to verify these effects through experiments because it is impossible to arrange the inter-particle angle. Therefore, in this study, the force transmission mechanism was simulated in the compaction process using FEM simulation. To examine the contact angle and force transmission between the particles, a green compact was modeled as individual particles rather than as a continuum green compact. Finally, it was confirmed through analysis that the pressure transmission between the particles remained constant during the compression process.11Ysciescopu
Ruthenium anchored on carbon nanotube electrocatalyst for hydrogen production with enhanced Faradaic efficiency
Developing efficient and stable electrocatalysts is crucial for the electrochemical production of pure and clean hydrogen. For practical applications, an economical and facile method of producing catalysts for the hydrogen evolution reaction (HER) is essential. Here, we report ruthenium (Ru) nanoparticles uniformly deposited on multi-walled carbon nanotubes (MWCNTs) as an efficient HER catalyst. The catalyst exhibits the small overpotentials of 13 and 17 mV at a current density of 10 mA cm(-2) in 0.5M aq. H2SO4 and 1.0M aq. KOH, respectively, surpassing the commercial Pt/C (16 mV and 33 mV). Moreover, the catalyst has excellent stability in both media, showing almost "zeroloss" during cycling. In a real device, the catalyst produces 15.4% more hydrogen per power consumed, and shows a higher Faradaic efficiency (92.28%) than the benchmark Pt/C (85.97%). Density functional theory calculations suggest that Ru-C bonding is the most plausible active site for the HER
Unified Hierarchical Relationship Between Thermodynamic Tradeoff Relations
Recent years have witnessed a surge of discoveries in the studies of
thermodynamic inequalities: the thermodynamic uncertainty relation (TUR) and
the entropic bound (EB) provide a lower bound on the entropy production (EP) in
terms of nonequilibrium currents; the classical speed limit (CSL) expresses the
lower bound on the EP using the geometry of probability distributions; the
power-efficiency (PE) tradeoff dictates the maximum power achievable for a heat
engine given the level of its thermal efficiency. In this study, we show that
there exists a unified hierarchical structure encompassing all of these bounds,
with the fundamental inequality given by a novel extension of the TUR (XTUR)
that incorporates the most general range of current-like and state-dependent
observables. By selecting more specific observables, the TUR and the EB follow
from the XTUR, and the CSL and the PE tradeoff follow from the EB. Our
derivations cover both Langevin and Markov jump systems, with the first proof
of the EB for the Markov jump systems and a more generalized form of the CSL.
We also present concrete examples of the EB for the Markov jump systems and the
generalized CSL.Comment: 19 pages, 4 figure
In situ Polymerization of Multi-Walled Carbon Nanotube/Nylon-6 Nanocomposites and Their Electrospun Nanofibers
Multiwalled carbon nanotube/nylon-6 nanocomposites (MWNT/nylon-6) were prepared by in situ polymerization, whereby functionalized MWNTs (F-MWNTs) and pristine MWNTs (P-MWNTs) were used as reinforcing materials. The F-MWNTs were functionalized by Friedel-Crafts acylation, which introduced aromatic amine (COC6H4-NH2) groups onto the side wall. Scanning electron microscopy (SEM) images obtained from the fractured surfaces of the nanocomposites showed that the F-MWNTs in the nylon-6 matrix were well dispersed as compared to those of the P-MWNTs. Both nanocomposites could be electrospun into nanofibers in which the MWNTs were embedded and oriented along the nanofiber axis, as confirmed by transmission electron microscopy. The specific strength and modulus of the MWNTs-reinforced nanofibers increased as compared to those of the neat nylon-6 nanofibers. The crystal structure of the nylon-6 in the MWNT/nylon-6 nanofibers was mostly γ-phase, although that of the MWNT/nylon-6 films, which were prepared by hot-pressing the pellets between two aluminum plates and then quenching them in icy water, was mostly α-phase, indicating that the shear force during electrospinning might favor the γ-phase, similarly to the conventional fiber spinning
Knowledge-Augmented Language Model Verification
Recent Language Models (LMs) have shown impressive capabilities in generating
texts with the knowledge internalized in parameters. Yet, LMs often generate
the factually incorrect responses to the given queries, since their knowledge
may be inaccurate, incomplete, and outdated. To address this problem, previous
works propose to augment LMs with the knowledge retrieved from an external
knowledge source. However, such approaches often show suboptimal text
generation performance due to two reasons: 1) the model may fail to retrieve
the knowledge relevant to the given query, or 2) the model may not faithfully
reflect the retrieved knowledge in the generated text. To overcome these, we
propose to verify the output and the knowledge of the knowledge-augmented LMs
with a separate verifier, which is a small LM that is trained to detect those
two types of errors through instruction-finetuning. Then, when the verifier
recognizes an error, we can rectify it by either retrieving new knowledge or
generating new text. Further, we use an ensemble of the outputs from different
instructions with a single verifier to enhance the reliability of the
verification processes. We validate the effectiveness of the proposed
verification steps on multiple question answering benchmarks, whose results
show that the proposed verifier effectively identifies retrieval and generation
errors, allowing LMs to provide more factually correct outputs. Our code is
available at https://github.com/JinheonBaek/KALMV.Comment: EMNLP 202
Analysis of Slab and Slab Heater Cover in a Compact Endless Cast and Rolling Mill Process using Finite Element Methods
Compact Endless cast and rolling Mill (CEM) processes were developed and used to fabricate steel products such as steel slabs. However, the coiling furnace in this process was very expensive, so a new layout was suggested. As the coiling furnace was removed, the interval among the slab heaters had to be increased. This led to a temperature drop in the slab. The temperature distribution of the slab impacts quality, so new layout was developed. This paper presents a Finite Element Method (FEM) simulation of thermal behavior in the slab employing slab heater covers. All of the simulation results were verified by comparing them with experimental results. The slab moving distance at which the temperature was saturated during the process was determined to consider the steady-state and analyze the temperature distribution of the slab and slab heater. Those results revealed that the efficiency of heat conservation increased by more than 50% using the slab heater cover. Finally, a sensitivity analysis of the slab heater cover was conducted with respect to the cover design. The effects of insulator thickness, the gap distance between the slab and cover, and material parameters such as density, and specific heat were investigated to optimize the design of the slab heater cover to produce the best quality slab.11Ysciescopuskc
Ectopic adrenal gland tissue in the left ovary of an elderly woman: a case report
Ectopic adrenal gland in the ovary is very rare case, and even more rarer in older women. We reported a case of ectopic adrenal tissue as an incidental finding in left ovary from a 68-year-old woman. She presented with bearing down sensation due to uterine prolapse for 5 years. Upon physical examination, uterine prolapse grade III, cystocele, and rectocele were observed. Ultrasonography findings showed 0.69 cm intramural myoma, and no specific findings were found in the bilateral adnexae. She underwent a total laparoscopic hysterectomy, bilateral salpingo-oophorectomy, and anterior-posterior repair. The final pathologic diagnosis of the case was ectopic adrenal gland tissue in the left ovary and uterine leiomyoma. No eventful reactions were observed during hospitalization and after discharge. Although ectopic adrenal gland rarely occurs in elderly women and in the pelvic ovaries, it has a risk of neoplastic transformation and accompanying germ cell tumor and sex cord tumor. Hence, if the ectopic adrenal gland tissue is suspected during surgery, the tissue should be removed. Additionally, by closely examining the contralateral ovary, determining whether other lesions are suspected is necessary. If the other lesions including germ cell tumor or sex cord tumor are suspected, a biopsy of the contralateral ovarian tissue should be performed. Thus, gynecologists must have knowledge about ectopic adrenal gland tissues
The impact of dose of the angiotensin-receptor blocker valsartan on the post-myocardial infarction ventricular remodeling: study protocol for a randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Angiotensin-converting enzyme inhibitors and the angiotensin-receptor blocker valsartan ameliorate ventricular remodeling after myocardial infarction (MI). Based on previous clinical trials, a maximum clinical dose is recommended in practical guidelines. Yet, has not been clearly demonstrated whether the recommended dose is more efficacious compared to the lower dose that is commonly used in clinical practice.</p> <p>Method/Design</p> <p>Valsartan in post-MI remodeling (VALID) is a randomized, open-label, single-blinded multicenter study designed to compare the efficacy of different clinical dose of valsartan on the post-MI ventricular remodeling. This study also aims to assess neurohormone change and clinical parameters of patients during the post-infarct period. A total of 1116 patients with left ventricular dysfunction following the first episode of acute ST-elevation MI are to be enrolled and randomized to a maximal tolerable dose (up to 320 mg/day) or usual dose (80 mg/day) of valsartan for 12 months in 2:1 ratio. Echocardiographic analysis for quantifying post-MI ventricular remodeling is to be conducted in central core laboratory. Clinical assessment and laboratory test are performed at fixed times.</p> <p>Discussion</p> <p>VALID is a multicenter collaborative study to evaluate the impact of dose of valsartan on the post-MI ventricular remodeling. The results of the study provide information about optimal dosing of the drug in the management of patients after MI. The results will be available by 2012.</p> <p>Trial registration</p> <p><a href="http://www.clinicaltrials.gov/ct2/show/NCT01340326">NCT01340326</a></p
Cochlear Implantation after Bilateral Transverse Temporal Bone Fractures
Patients deafened by a severe head injury are rarely encountered. We report a case of a 65-yr-old man with bilateral transverse temporal bone fractures due to head injury. He underwent cochlear implant and achieved a satisfactory auditory rehabilitation. Imaging studies of temporal bone before performing a cochlear implantation provide important information on a patient with bilateral temporal bone fractures. Cochlear implantations with careful planning in such a patient may be a very effective method for aural rehabilitation
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