Experimental investigation on up-flow boiling of R1234yf in aluminum multi-port extruded tubes

The local characteristics of heat transfer and pressure drop were investigated experimentally for the vertical upflow boiling of low GWP refrigerant R1234yf in two types of aluminum multi-port extruded tubes having 16 channels with a cross section of 0.9×0.2 mm2 and 40 channels with a cross section of 0.3×0.2 mm2 respectively. At an evaporating temperature of 15 ℃, the local heat transfer coefficient and pressure drop at heat flux of 4-16 kW/m2 and mass flux of 60-240 kg/(m2s) were measured. Combined with previous results of multi-port extruded tubes having 16 channels with a cross section of 0.9×0.9 mm2, the effect of tube dimension on boiling heat transfer was reported. In addition, based on the heat transfer coefficient at various heat flux and mass flux, the boiling heat transfer mechanism was briefly analyzed.

Flow Boiling Heat Transfer of Binary Mixtures HFO1234yf/R32 in a Smooth Horizontal Tube

HFO1234yf is a promising alternative for automobile air conditioners because of its low GWP of 4 and thermophysical properties similar to those of R134a. However, its performance is inferior to R410A. This makes it difficult to be applied to residential air-conditioners. A mixture of HFO1234yf and R32 is expected to balance both the GWP and COP requirement when applied to residential air-conditioning systems. In this study, flow boiling heat transfer coefficients of HFO1234yf and R32 (80:20 and 50:50 by wt%) were measured in a smooth horizontal tube at a saturation temperature of 15°C. The inner diameter (ID) of the test section is 4 mm. The mass flux ranges from 100 to 300 kg/m2·s, and the heat flux changes from 6 to 24 kW/m2. Heat transfer coefficients of the mixtures and pure HFO1234yf were summarized at three Bo numbers. The influence of Bo on mass discussion was observed and discussed. It is found that there is notable influence of mass diffusion on heat transfer when Bo is large. When Bo is small, the convective heat transfer at high vapor qualities seems to be suppressed due to the effects of mass diffusion. Results show that the heat transfer coefficient of the 50:50 wt% mixture of HFO1234yf and R32 is higher than that of the 80:20 wt% mixture and is also the same or even higher than that of pure HFO1234yf. A theoretical model was proposed to predict the heat transfer coefficients of the mixtures HFO1234yf and R32 under two concentrations. The prediction model can catch 80% of the data within deviation of ±20%

Performance-based seismic isolation design using the theory of spatially concave friction distribution

Seismic isolation devices were designed to protect three similar building structures, containing different objects with different fragilities, in a strong earthquake region. And a performance-based assessment framework, established by the PEER, was used to identify the seismic isolation efficiency of these devices. It optimized the ratios of spring part, viscous damping part and friction part in the seismic isolation devices, aiming at different functional buildings. Results show that a spatially concave friction distribution, combined with a weak spring, not only can reduce the structural acceleration response during earthquakes, but also decrease the structural residual displacement after earthquakes. Moreover, the spatially concave friction distribution can dissipate earthquake energy, but cannot hinder the recentering of structure like that of general uniform friction distributions. Consequently, the spatially concave friction distribution can partly or fully replace the viscous dampers, which are more expensive and short-lived. The reasonable combination of different components in the seismic isolation devices can satisfy different seismic requirements, aiming at different functional buildings

CORECODE: A Common Sense Annotated Dialogue Dataset with Benchmark Tasks for Chinese Large Language Models

As an indispensable ingredient of intelligence, commonsense reasoning is crucial for large language models (LLMs) in real-world scenarios. In this paper, we propose CORECODE, a dataset that contains abundant commonsense knowledge manually annotated on dyadic dialogues, to evaluate the commonsense reasoning and commonsense conflict detection capabilities of Chinese LLMs. We categorize commonsense knowledge in everyday conversations into three dimensions: entity, event, and social interaction. For easy and consistent annotation, we standardize the form of commonsense knowledge annotation in open-domain dialogues as "domain: slot = value". A total of 9 domains and 37 slots are defined to capture diverse commonsense knowledge. With these pre-defined domains and slots, we collect 76,787 commonsense knowledge annotations from 19,700 dialogues through crowdsourcing. To evaluate and enhance the commonsense reasoning capability for LLMs on the curated dataset, we establish a series of dialogue-level reasoning and detection tasks, including commonsense knowledge filling, commonsense knowledge generation, commonsense conflict phrase detection, domain identification, slot identification, and event causal inference. A wide variety of existing open-source Chinese LLMs are evaluated with these tasks on our dataset. Experimental results demonstrate that these models are not competent to predict CORECODE's plentiful reasoning content, and even ChatGPT could only achieve 0.275 and 0.084 accuracy on the domain identification and slot identification tasks under the zero-shot setting. We release the data and codes of CORECODE at https://github.com/danshi777/CORECODE to promote commonsense reasoning evaluation and study of LLMs in the context of daily conversations.Comment: AAAI 202

Is propofol injection pain really important to patients?

BACKGROUND: Propofol injection pain (PIP) has been adequately studied during the past decades. However, patients’ opinion on this problem and the incidence of patients’ recall of this brief discomfort are still unknown. Thus, we conducted this study to know the patients’ perspectives on PIP and provide useful information about the incidence of recall of PIP under our routine general anesthesia. METHODS: Five hundred preoperative questionnaires were distributed to patients who were scheduled for elective open thyroidectomy under general anesthesia from May 2016 to July 2016. They were asked to rank ten possible adverse effects associated with general anesthesia from their most undesirable to their least undesirable effect. Patients who completed the preoperative questionnaires were asked whether they could recall PIP and to grade the severity of PIP on the first postoperative day. RESULTS: A total of 448 preoperative questionnaires were returned and analyzed with an efficient rate of 89.6%. Incisional pain was ranked as most undesirable, followed (in order) by vomiting, gagging on the tracheal tube, nausea, sore throat, propofol injection pain, shivering, intravenous puncture pain, and anxiety. The majority (91.5%) of surveyed patients could not recall any discomfort or pain during anesthetics injection. Of those who could recall PIP, 89.5% grade it as mild pain, 7.9% moderate pain, and 2.6% severe pain. CONCLUSIONS: Most of patients undergoing elective open thyroidectomy in our hospital viewed PIP as a relatively minor problem. The incidence of recall of PIP was low and the majority of those who recalled regarded it as mild, temporary and acceptable pain. However, further investigations into propofol injection pain may be warranted as patients’ perspectives on propofol injection pain and its severity may differ between patient populations

Voltage control strategy of a high-permeability photovoltaic distribution network based on cluster division

The use of distributed photovoltaics (PVs) on a large scale often causes voltage over-limit problems in distribution networks. This paper proposes a distributed photovoltaic cluster collaborative optimization voltage control strategy based on an improved community algorithm to address the issue of centralized control being unable to respond quickly to the randomness of distributed photovoltaics and the difficulty of achieving overall coordination with local control. First, by improving the community algorithm, the division of reactive and active clusters, considering the power balance and node coupling degree, is realized. Then, the cluster-coordinated voltage control strategy is proposed by making full use of the power control ability of a photovoltaic inverter. Finally, a voltage regulation ability evaluation index is proposed to assess the node regulation ability within the cluster and select key nodes. This effectively reduces the number of control nodes. The simulation analysis of the improved IEEE 69 distribution network shows that the proposed voltage control strategy can mitigate the issue of voltage over-limit in high-permeability distributed photovoltaic access distribution and enhance the photovoltaic consumption capacity