Entropy generation and thermal performance of a pulsating heat pipe

Title from PDF of title page; abstract from research PDF (University of Missouri--Columbia, viewed on June 26, 2014).A U-shaped pulsating heat pipe is an excellent heat transfer performance device. This study has been investigated step by step. a) The entropy generation is based on the second law of thermodynamics. In the present study, the entropy generation in a U-shaped Pulsating Heat Pipe (PHP) is numerically investigated. The following five parameters, which are vapor mass, liquid temperature, latent heat, sensible heat, and friction, determine the entropy generation. The results show that the entropy generation is significantly affected by the initial temperature in the PHP. Particularly, the variation of the vapor mass is a primary factor of the entropy generation. On the other hand, the amplitude of the entropy generation is barely related with the pressure loss at the bend in the PHP. However, the frequency of the entropy generation with the pressure loss is faster than that without the pressure loss at the bend. b) Pulsating heat pipe is a two-phase heat transfer device that transfers heat from heating section to cooling section via oscillatory liquid-vapor two-phase flow. The temperatures of heating and cooling sections are extremely important parameters, and play significant roles for the performance of pulsating heat pipes. The objective of this work is to study the effects of fluctuations of heating and cooling section temperatures on the oscillatory flow, temperature and pressure of the vapor plugs, as well as latent and sensible heat transfer of a pulsating heat pipe. The fluctuations of wall temperatures include a periodic component and a random component. The periodic component is characterized by the amplitude and frequency, while the random component is described by the standard deviation. The performance of the pulsating heat pipe is evaluated at various amplitudes, frequencies and standard deviations of the fluctuations. c) A numerical study is performed to investigate heat transfer performance and effect of nanofluids on a pulsating heat pipe (PHP). Pure water is employed as the base fluid while Al2O3 with two different particle sizes, 38.4 and 47 nm, is used as nanoparticle. Different parameters including displacement of liquid slug, vapor temperature and pressure, liquid slug temperature distribution, as well as sensible and latent heat transfer in evaporator and condenser are calculated numerically and compared with the ones for pure water as working fluid. The results show that nanofluid has significant effect on heat transfer enhancement of the system and with increasing volume fraction and decreasing particles diameter the enhancement intensifies

DNA multi-bit non-volatile memory and bit-shifting operations using addressable electrode arrays and electric field-induced hybridization.

DNA has been employed to either store digital information or to perform parallel molecular computing. Relatively unexplored is the ability to combine DNA-based memory and logical operations in a single platform. Here, we show a DNA tri-level cell non-volatile memory system capable of parallel random-access writing of memory and bit shifting operations. A microchip with an array of individually addressable electrodes was employed to enable random access of the memory cells using electric fields. Three segments on a DNA template molecule were used to encode three data bits. Rapid writing of data bits was enabled by electric field-induced hybridization of fluorescently labeled complementary probes and the data bits were read by fluorescence imaging. We demonstrated the rapid parallel writing and reading of 8 (23) combinations of 3-bit memory data and bit shifting operations by electric field-induced strand displacement. Our system may find potential applications in DNA-based memory and computations

Towards Suicide Prevention from Bipolar Disorder with Temporal Symptom-Aware Multitask Learning

Bipolar disorder (BD) is closely associated with an increased risk of suicide. However, while the prior work has revealed valuable insight into understanding the behavior of BD patients on social media, little attention has been paid to developing a model that can predict the future suicidality of a BD patient. Therefore, this study proposes a multi-task learning model for predicting the future suicidality of BD patients by jointly learning current symptoms. We build a novel BD dataset clinically validated by psychiatrists, including 14 years of posts on bipolar-related subreddits written by 818 BD patients, along with the annotations of future suicidality and BD symptoms. We also suggest a temporal symptom-aware attention mechanism to determine which symptoms are the most influential for predicting future suicidality over time through a sequence of BD posts. Our experiments demonstrate that the proposed model outperforms the state-of-the-art models in both BD symptom identification and future suicidality prediction tasks. In addition, the proposed temporal symptom-aware attention provides interpretable attention weights, helping clinicians to apprehend BD patients more comprehensively and to provide timely intervention by tracking mental state progression.Comment: KDD 2023 accepte

Influence of MWCNTs on β

The surface of multiwalled carbon nanotubes (MWCNTs) was chemically modified using 1-pyrenebutyric acid (PBA) to improve its compatibility with polyvinylidene fluoride (PVDF). The carboxylic acid groups of the MWCNTs-PBA (PCNTs) provide a β-phase nucleation site to the fluorine of PVDF along their surface. The content of the β-phase crystalline structure of PVDF was found to be the highest at a concentration of 1.0 wt.% of PCNTs, and these PVDF-PCNTs composites were utilized as active layers in triboelectric devices. The maximum output voltage achieved was 16 volts at a concentration of 1.0 wt.% of PCNTs in the PVDF composites

Solution-Processed Vertically Stacked Complementary Organic Circuits with Inkjet-Printed Routing

The fabrication and measurements of solution-processed vertically stacked complementary organic field-effect transistors (FETs) with a high static noise margin (SNM) are reported. In the device structure, a bottom-gate p-type organic FET (PFET) is vertically integrated on a top-gate n-type organic FET (NFET) with the gate shared in-between. A new strategy has been proposed to maximize the SNM by matching the driving strengths of the PFET and the NFET by independently adjusting the dielectric capacitance of each type of transistor. Using ideally balanced inverters with the transistor-on-transistor structure, the first examples of universal logic gates by inkjet-printed routing are demonstrated. It is believed that this work can be extended to large-scale complementary integrated circuits with a high transistor density, simpler routing path, and high yield

Clinical characteristics and serum N-terminal pro-brain natriuretic peptide as a diagnostic marker of Kawasaki disease in infants younger than 3 months of age

PurposeThe incidence of Kawasaki disease (KD) is rare in young infants (less than 3 months of age), who present with only a few symptoms that fulfill the clinical diagnostic criteria. The diagnosis for KD can therefore be delayed, leading to a high risk of cardiac complications. We examined the clinical characteristics and measured the serum levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) levels of these patients for assessing its value in the early detection of KD.MethodsWe retrospectively reviewed the data of young infants diagnosed with KD from 2004 to 2012. The control group included 20 hospitalized febrile patients. Laboratory data, including NT-proBNP were obtained for each patient in both groups.ResultsIncomplete KD was observed in 21/24 patients (87.5%). The mean fever duration on admission was 1.36±1.0 days in the KD group. Common symptoms included erythema at the site of Bacille Calmette-Guerin inoculation (70.8%), skin rash (50.0%), changes of oropharyngeal mucosa (29.1%), and cervical lymphadenopathy (20.8%). The mean number of major diagnostic criteria fulfilled was 2.8±1.4. Five KD patients (20.8%) had only one symptom matching these criteria. The incidence of coronary artery complications was 12.5%. The mean serum NT-proBNP level in the acute phase, in the KD and control groups, were 4,159±3,714 pg/mL and 957±902 pg/mL, respectively, which decreased significantly in the convalescent phase.ConclusionIncomplete KD was observed in 87.5% patients. Serum NT-proBNP might be a valuable biomarker for the early detection of KD in febrile infants aged <3 months

Uveitis as an important ocular sign to help early diagnosis in Kawasaki disease

PurposeIncomplete Kawasaki disease (KD) is frequently associated with delayed diagnosis and treatment. Delayed diagnosis leads to increasing risk of coronary artery aneurysm. Anterior uveitis is an important ocular sign of KD. The purpose of this study was to assess differences in laboratory findings, including echocardiographic measurements, clinical characteristics such as fever duration and treatment responses between KD patients with and those without uveitis.MethodsWe conducted a prospective study with 110 KD patients from January 2008 to June 2013. The study group (n=32, KD with uveitis) was compared with the control group (n=78, KD without uveitis). Laboratory data were obtained from each patient including complete blood count (CBC), erythrocyte sedimentation rate (ESR), platelet count, and level of alanine aminotransferase, aspartate aminotransferase, serum total protein, albumin, C-reactive protein (CRP), and N-terminal probrain natriuretic peptide (NT-pro BNP). Echocardiographic measurements and intravenous immunoglobulin responses were compared between the two groups.ResultsThe incidence of uveitis was 29.0%. Neutrophil counts and patient age were higher in the uveitis group than in the control group. ESR and CRP level were slightly increased in the uveitis group compared with the control group, but the difference between the two groups was not significant. No significant differences in coronary arterial complication and treatment responses were observed between the two groups.ConclusionUveitis is an important ocular sign in the diagnosis of incomplete KD. It is significantly associated with patient age and neutrophil count