Steep Balmer decrement in weak AGNs may be not caused by dust extinction: clues from low-luminosity AGNs and changing-look AGNs

The hydrogen Balmer decrement (e.g., $\rm H\alpha/H\beta$) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs (LLAGNs) and changing-look AGNs (CLAGNs), which have steep Balmer decrement but without strong evidence for absorption. We compile a sample of normal AGNs and CLAGNs with a wider distribution of bolometric Eddington ratio ($\lambda_{\rm Edd}=L_{\rm bol}/L_{\rm Edd}$) and find a strong negative correlation between $\rm H\alpha/H\beta$ and $\lambda_{\rm Edd}$, which suggests that the Balmer decrement is also accretion-rate dependent. We further explore the Balmer decrement based on the photoionization model using the Cloudy code by considering spectral energy distribution (SED) from the accretion disk with different accretion rates (e.g., disk/corona and truncated disk at high and low Eddington ratios, respectively). Both the standard disk and truncated disk predict a negative correlation of $\rm H\alpha/H\beta-\lambda_{\rm Edd}$, where the relation is steeper in the case of the truncated disk. The negative correlations are also explored in two single CLAGNs. The measured negative correlation of $\rm H\alpha/H\beta$ -- $\lambda_{\rm Edd}$ is mainly caused by the lower responsivity $({\rm dlog}L_{\rm line}/{\rm dlog}L_{\rm cont})$ in $\rm H\alpha$ relative to that in $\rm H\beta$, due to the larger optical depth in the former. We propose that the steep Balmer decrements in low-Eddington-ratio AGNs (e.g., some Seyferts 1.5-1.9 and CLAGNs) are not simply caused by absorption but mainly caused by the relatively low flux of ionizing photons.Comment: 13 pages, 3 figures, Accepted for publication in The Astrophysical Journa

A study on the thought of Qing (情) in the Zhuang Zi

The concept of “qíng” 情is an important concept in Chinese philosophy and can be found throughout pre-Qin classical literature. Among them, Zhuāngzi is particularly prominent in its discussion of “qíng” and “xìng” 性, with a large amount of related material. However, currently, there is relatively little attention paid to Taoist “human nature theory,” especially the “xìngqíng theory,” and a large amount of the material in Zhuāngzi related to “xìng” and “qíng” has not received the corresponding attention. Therefore, this article takes the possible contradiction in the debate between Zhuangzi and Huizi at the end of the “Déchōngfú”（《德充符》）chapter regarding detachment from likes and dislikes (wú qíng无情) as the problem consciousness. Using the entire text of Zhuāngzi as the research content, it studies the concept of “qíng” in Zhuāngzi and step by step, starting from the discussion of pre-Qin thought on “qíng” to the exploration of the specific implications of “wú qíng” (detachment from likes and dislikes) in Zhuāngzi, gradually focusing on the topic of “qíng” in Zhuāngzi. The first chapter, “Unpacking the Meaning of Qíng, “delves into the development of the concept of “qíng” and its textual implications over various historical periods. Drawing from pre-Qin literature, this chapter investigates how “qíng” originally derived from the meanings of “essence” and eventually developed into four meaning categories: “xìng” 性 (human nature), “qíng shí” 情实 (innate characteristics), “qíng gǎn” 情感 (sentimental emotions), and “zhēn chéng” 真诚 (sincerity). These four categories can be simplified into two fundamental meanings: “qíng shí” and “qíng gǎn.” The chapter also examines the links and distinctions between “qíng” and “dào” 道 (the Way), “qíng” and “xìng” (human nature), and “qíng” and “yù” 欲 (desire), placing them within a broad temporal and spatial context. By defining the scope of the “qíng” concept, this chapter offers a solid foundation for comprehending the meaning of “qíng” in Zhuāngzi. In Chapter 2, this paper delves into the concept of “qíng” in the Zhuāngzi. There are two fundamental uses of “qíng” in the text: “qíng shí” (innate characteristics) and “qíng gǎn” (sentimental emotions). From there, this paper explores the four critical ideas under “qíng shí”, including “tiān zhī qíng” 天之情, “xìng zhī qíng” 性之情,c“wù zhī qíng” 物之情, and “rén zhī qíng” 人之情. “Tiān zhī qíng” denotes the innate and natural order that regulates all things in the world. It represents the inherent functioning mechanism. “Xìng zhī qíng” refers to the inherent and authentic nature of all things and living beings, which is innate and naturally endowed. Zhuāngzi defines “wù zhī qíng” from the perspective that it cannot be completely altered or fully grasped by humans. This implies that the nature of things is beyond human control and understanding. “Rén zhī qíng” refers to the nature and essence of humans, which is natural and inherent. Its characteristics include the primordial nature, benevolence, righteousness, desires, and emotions. These are inherent aspects of human nature, which shape or influence our beliefs, values, and behaviors. On the other hand, with regards to the “qíng” (emotions/affections), this article categorizes the emotions discussed in Zhuāngzi into three types based on social roles: the affection between parents and children, spouses, and friends. Each type of emotion has its unique features. As a result, the paper emphasizes a notable discussion between Zhuangzi and his disciple Huizi on the existence of emotions in the chapter “Déchōngfú”. The debate revolves around the notion that “rén gù wú qíng” 人固无情 (humans are devoid of emotions). However, the concept of “wú qíng” (detachment from likes and dislikes) in Zhuāngzi’s philosophy does not imply that humans should be emotionless. Therefore, the paper focuses on Zhuāngzi’s perspective on how we should approach our emotions. This is a key factor that the paper addresses. In Chapter 3, titled “Detachment from Likes and Dislikes and True Emotions in the Absence of Emotions”, this chapter delves into discussions on personal cultivation. The chapter emphasizes that “wú qíng” (detachment from likes and dislikes) should be taken as a whole. The paper explains that “wú qíng” in the Zhuāngzi refers to the idea that a man doesn't allow likes or dislikes to get in and do him harm. He just lets things be the way they are and doesn't try to help life along. (人之不以好恶内伤其身，常因自然而不益生也) On the one hand, “not harming oneself with likes and dislikes” can be understood as being “without material desire”, and not being greedy for material possessions. On the other hand, “not benefiting oneself by acting against true nature” can be understood as being “without human deceit.” The realization of “control of material desire and human deceit” leads to the realization of “true emotions.” “True emotions” is further divided into two parts. The first part, “making it be spring with everything” means that regardless of external changes, one’s emotional state remains constant, like the cheerful and pleasant days of spring. One does not become caught up in desire for material possessions, and therefore does not harm oneself or others. The second part, “using the mind like a mirror,” refers to reflecting the natural state of oneself, nature, and time. By being in harmony with the natural world, one can calmly and naturally adapt to changes, without being overly reactive or attached. It should be noted that only those who have attained enlightenment can reach such a state. This statement emphasizes that the realm is a state of being that is beyond the reach of most people. It is only through the attainment of enlightenment that one can achieve the harmony with the natural world and the inner peace required to reach this state. The following is Chapter 4, which discusses how Zhuangzi cultivation theory can be relevant to ordinary people, common people, and others. This chapter emphasizes the concept of “Nà Qíng” (receptivity and attainment of emotions). “Receptivity” means acknowledging and accepting the existence of negative emotions. It requires individuals to let go of their obsession with emotionlessness, abandon the insistence on preserving the natural and simple nature of things, and avoid the secondary harm of “harming oneself emotionally.” By minimizing their attention to negative emotions and achieving tranquility, individuals can create the possibility of attaining emotions. “Dá Qíng” (achieving emotional harmony) means understanding the nature of life, destiny, and personality, and using cognition to control emotions. By changing one’s perception of the world, inner peace and tranquility can be achieved. The concept of “dá qíng” (achieving emotional harmony) can be further divided into three aspects: First, there is the “Attainment of Emotions of Life.” This refers to an individual’s understanding of the nature of life and death, recognizing that death is inevitable and that life entails labor and rest. By accepting and embracing life and death, individuals can achieve a good death and a good life. Second is the “attainment of emotions of destiny.” This involves understanding the nature of destiny and developing a carefree and heroic attitude towards it. After realizing that destiny is unchangeable, individuals should show respect, forgetfulness, acceptance, and understanding towards their own destiny, attaining a sense of detachment from it. Finally, we have the “Attainment of Emotions of Personality.” This entails understanding one's innate nature and the genuine emotions that arise from it. By reflecting on the negative emotional disturbances of daily life, individuals should strive to “do nothing,” reducing any harm inflicted upon their natural character that could lead to emotional depletion. By doing so, individuals can attain a connection with nature and their true emotions, and rediscover their innate nature and true selves. The concept of “qíng” in the Zhuāngzi goes beyond its ordinary meaning, as it encompasses a range of important philosophical and existential issues. Through exploring topics such as “Dào道”, “Tiān 天” (Heaven), “Xìng” (Nature), “Yù”(Desire), “Destiny”, the study of “qíng” in the Zhuāngzi has significant implications for Taoist philosophy. Furthermore, Zhuangzi's emphasis on emotions has had a profound influence on later generations, particularly in the Wei and Jin periods, where scholars greatly valued and expressed their emotions. The book's promotion of leisure, tranquility, naturalness, and authenticity of emotions is inspiring and has practical relevance for individuals seeking nourishment from within. Thus, the study of “qíng” in the Zhuāngzi is not limited to a cursory analysis of emotions but is a comprehensive philosophical enterprise, which has broad implications for our understanding of human nature, existence, and spiritual development

Steep Balmer Decrement in Weak AGNs May Not Be Caused by Dust Extinction: Clues from Low-luminosity AGNs and Changing-look AGNs

The hydrogen Balmer decrement (e.g., H α /H β ) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs and changing-look AGNs (CLAGNs), which have steep Balmer decrement but without strong evidence for absorption. We compile a sample of normal AGNs and CLAGNs with a wider distribution of bolometric Eddington ratio ( λ _Edd = L _bol / L _Edd ) and find a strong negative correlation between H α /H β and λ _Edd , which suggests that the Balmer decrement is also accretion-rate dependent. We further explore the Balmer decrement based on the photoionization model using the Cloudy code by considering spectral energy distribution from the accretion disk with different accretion rates (e.g., disk/corona and truncated disk at high and low Eddington ratios, respectively). Both the standard disk and truncated disk predict a negative correlation of H α /H β – λ _Edd , where the relation is steeper in the case of the truncated disk. The negative correlations are also explored in two single CLAGNs. The measured negative correlation of H α /H β – λ _Edd is mainly caused by the lower responsivity $(d\mathrm{log}{L}_{\mathrm{line}}/d\mathrm{log}{L}_{\mathrm{cont}})$ in H α relative to that in H β due to the larger optical depth in the former. We propose that the steep Balmer decrements in low Eddington ratio AGNs (e.g., some Seyferts 1.5–1.9 and CLAGNs) are not simply caused by absorption but mainly caused by the relatively low flux of ionizing photons

The Physical Properties of Changing-look Blazars

Changing-look active galactic nuclei (AGNs) are a special class of AGNs that change their spectral type from type 1 to type 2 or vice versa. In recent years, a number of changing-look blazars (CLBs) were also reported, which transition between flat-spectrum radio quasars and BL Lacs. The physical properties of CLBs are still unclear. Using the mclust R package for Gaussian mixture modeling, we performed a clustering analysis for a sample of 105 CLBs selected from the literature. Three kinds of analysis found that CLBs lie in between the parameter distributions of FSRQs and BL Lacs: (i) univariate analysis; (ii) bivariate analysis; and (iii) multivariate analysis, carried out with a dimension reduction approach of the physical properties of the three types of blazars. Our results suggest that CLBs belong to a transition type between FSRQs and BL Lacs, which may be regulated by the change of accretion process and may be similar to other changing-look AGNs

Effect of the Current on the Fire Characteristics of Overloaded Polyvinyl Chloride Copper Wires

In this study, the fire behavior variation of unenergized polyvinyl chloride (PVC) copper wires subjected to overload with different currents was investigated by a cone calorimeter. Overload currents were selected from 1 times safe-rated current (Ie) to 3.5 times Ie to obtain tested sample wires. The mass fraction, time to ignition (TTI), heat release rate (HRR), gas emission, and residue were measured. If the current flowing through the wire increased up to 3.5 times Ie, the TTI of this unenergized wire increased drastically and the peak HRR (pHRR) decreased notably so that the flame growing index (FGI) reduced considerably. When the wire carried less than three times Ie, the FGI remained stable. For all overloaded PVC copper wires, the increase in the heat flux resulted in a higher pHRR and a lower burning duration. However, regardless of the external heat flux exposure, the FGI of copper wires overloaded at 3.5 times Ie was lower than that of copper wires carrying less than other times Ie. Moreover, the consumption of O2 and generation of CO2 as the heat flux varied were consistent with that of the HRR. Opposed to expectation, the flame propagation of unenergized PVC copper wires would decline in a fire, if the wire has been damaged by overload with some currents

Opportunities and Challenges for Construction Health and Safety Technologies under the COVID-19 Pandemic in Chinese Construction Projects

The Coronavirus disease 2019 (COVID-19) pandemic has resulted in significant delays and cost overrun in construction projects. The implementation of health and safety (H&S) technologies is one of the most important strategies to alleviate the adverse impacts of COVID-19 on the construction industry and help the industry adapt to the new normal. This study aims to evaluate the adoption of H&S technologies for pandemic management in the construction sector under the COVID-19 pandemic. Semi-structured interviews with eighteen practitioners engaged from construction companies and technology firms were conducted to collect their views on the driving forces and issues of the adoption of H&S technologies for pandemic management in Chinese construction projects. The results reveal that the major H&S technologies used included the health quick response (QR) code system, artificial intelligence (AI)-powered fever monitoring, and site access control system. These technologies were reported to be effective in preventing the spread of the pandemic in workplaces. The findings of the study amplify that the pandemic may serve as an acceleration of the adoption of H&S technologies in the construction sector. Other technologies, such as building information modeling, drones, AI-based safety monitoring, and robotics, however, were seldom used in the studied projects. The interviewees addressed several problems regarding the implementation of these technologies. High costs of technologies, a lack of client support, and disruptions to the normal work process were the main hurdles of the adoption of these technologies. The results indicated that the external influence factor—the COVID-19 pandemic—could considerably drive the use of H&S technologies, whereas the internal influence factors—cost and compatibility of technology—might be the major barriers to technology adoption. To encourage the wider use of H&S technologies in construction, the government is recommended to support the technology transformation by granting financial subsidies for costs involved in innovation adoption. Project owners may consider investing substantially in H&S technologies that can strengthen their resilient and innovative ability to adapt to the post-COVID-19 landscape. The present results will be useful to industry stakeholders and researchers interested in developing H&S technologies for combating the COVID-19 pandemic and future crises