121 research outputs found
Essential oil of Citrus hystrix DC.: A mini-review on chemical composition, extraction method, bioactivities, and potential applications in food and pharmaceuticals
Citrus hystrix DC. is a common herb in tropical regions. Its essential oils are now widely researched and applied because of their high economic value and safety for humans and are interesting materials for future trends. This review provides an extensive overview of the biological activities of C. hystrix essential oil, characterized predominantly by citronellal, ?-Pinene, sabinene, limonene, and terpinene-4-ol, which are deciding factors in antimicrobial, antioxidant, insect repellent, anti-tumor, and anti-inflammatory properties. Therefore, it is applied in the fields of food preservation and pharmaceuticals. However, these applications should consider the ratio of these components in the essential oil, which is variable when using materials from different parts of the plant and depending on the original location of the plant, growth stages, traditional or modern extraction methods, and pre-treatment methods
Concolic Testing Heap-Manipulating Programs
Concolic testing is a test generation technique which works effectively by
integrating random testing generation and symbolic execution. Existing concolic
testing engines focus on numeric programs. Heap-manipulating programs make
extensive use of complex heap objects like trees and lists. Testing such
programs is challenging due to multiple reasons. Firstly, test inputs for such
program are required to satisfy non-trivial constraints which must be specified
precisely. Secondly, precisely encoding and solving path conditions in such
programs are challenging and often expensive. In this work, we propose the
first concolic testing engine called CSF for heap-manipulating programs based
on separation logic. CSF effectively combines specification-based testing and
concolic execution for test input generation. It is evaluated on a set of
challenging heap-manipulating programs. The results show that CSF generates
valid test inputs with high coverage efficiently. Furthermore, we show that CSF
can be potentially used in combination with precondition inference tools to
reduce the user effort
Revisiting LARS for Large Batch Training Generalization of Neural Networks
LARS and LAMB have emerged as prominent techniques in Large Batch Learning
(LBL), ensuring the stability of AI training. One of the primary challenges in
LBL is convergence stability, where the AI agent usually gets trapped into the
sharp minimizer. Addressing this challenge, a relatively recent technique,
known as warm-up, has been employed. However, warm-up lacks a strong
theoretical foundation, leaving the door open for further exploration of more
efficacious algorithms. In light of this situation, we conduct empirical
experiments to analyze the behaviors of the two most popular optimizers in the
LARS family: LARS and LAMB, with and without a warm-up strategy. Our analyses
give us a comprehension of the novel LARS, LAMB, and the necessity of a warm-up
technique in LBL. Building upon these insights, we propose a novel algorithm
called Time Varying LARS (TVLARS), which facilitates robust training in the
initial phase without the need for warm-up. Experimental evaluation
demonstrates that TVLARS achieves competitive results with LARS and LAMB when
warm-up is utilized while surpassing their performance without the warm-up
technique
Total factor productivity and outsourcing: the case of Vietnamese small and medium sized enterprises
Purpose â The paper aims to investigate the difference in total factor productivity (TFP) among those firms with and without outsourcing in a developing country like Vietnam. Also, it explores the effect of outsourcing activities on total factor productivity with a specified concentration on the Vietnamese small and medium-sized enterprises (SMEs). Design/methodology/approach â The panel data set of SMEs used in this study was originated from biannual surveys conducted under the collaboration between educational organizations and government agencies: Stockholm School of Economics (SSE), Department of Economics â the University of Copenhagen, the Institution of Labor Studies and Social Affairs (ILSSA) in the Ministry of Labor, Invalids and Social Affairs (MOLISA). In this study, the model is developed based on the production function in accordance with the model of Girma and Görg (2004). The firmsâ TFP is the difference between the actual and the predicted output as with the approach by Levinsohn and Petrin (2003). Findings â This study finds out that firms with outsourcing have higher total factor productivity than those without outsourcing activities. In addition, the more firms spend on outsourcing, the higher total factor productivity they can gain. Outsourcing to SMEs in a developing country can significantly increase its TFP by means of either maintaining core competencies or searching external resources in conducting some internal activities. Originality/value â Although outsourcing has been widely applied by large firms, the research studying its impact on productivity at firm level is limited. Especially, this study can shed light on the impact for the case of SMEs in a developing economy
History and applications of concrete steel composite structure
The composite steel-and-concrete structure is a modern structure, combines the advantages of concrete and steel one. Nowadays, it is widely utilized all over the world but not much in Vietnam. Studying the history of formation and development is very meaningful in understanding and applying this type of structure in practice. This article focuses on presenting the formation and development of the composite structure and, at the same time, introduces the potential and applications of the composite structure to the current construction practice in Vietnam
HYDROGEN-PLASMA-TREATED NANO TIO2 FOR PHOTOCATALYTIC OXIDATION OF VOCS IN AIR STREAM
Unlike water treatment processes, the photocatalytic oxidation of VOCs in air stream exhibits many challenges. This study will develop the hydrogen-plasma-treated TiO2 with improvement in photocatalytic activity. The hydrogen-plasma-treatment was carried out in the non-thermal atmospheric pressure reactor at room temperature or above. The catalysts were prepared and analyzed by advanced techniques such as X-ray diffraction (XRD), scanning electro-microscopy (SEM) and transmission electro-microscopy (TEM). The photocatalytic activity of the catalyst has been investigated under UV light with various reaction conditions such as different initial toluene/formaldehyde concentrations and water content. Significantly, the conversion of toluene by a plasma-treated sample was 1.5 times higher than the bare TiO2 in a similar reaction condition
FLAVONOIDS ISOLATED FROM THE FLOWERS OF CAMELLIA CHRYSANTHA
Camellia chrysantha (the golden camellia, golden tea) is a species of evergreen shrub or small tree belonging to the family Theaceae. The flowers and the leaves of this plant are used as tea and drank for its health benefits. The aim of this study was to investigate the chemical constituents of the flowers of Camellia chrysantha. Five flavonoids were isolated from the flowers of Camellia chrysantha (Theaceae), including (+)-catechin (1), (-)-epicatechin (2), quercetin (3), quercetin-3-O-methyl ether (4) and kaempferol (5). Their chemical structures were elucidated by spectroscopic data analysis and by comparison with those reported in the literature. Among five compounds, compounds 4 was isolated for the first time from this species
Label driven Knowledge Distillation for Federated Learning with non-IID Data
In real-world applications, Federated Learning (FL) meets two challenges: (1)
scalability, especially when applied to massive IoT networks; and (2) how to be
robust against an environment with heterogeneous data. Realizing the first
problem, we aim to design a novel FL framework named Full-stack FL (F2L). More
specifically, F2L utilizes a hierarchical network architecture, making
extending the FL network accessible without reconstructing the whole network
system. Moreover, leveraging the advantages of hierarchical network design, we
propose a new label-driven knowledge distillation (LKD) technique at the global
server to address the second problem. As opposed to current knowledge
distillation techniques, LKD is capable of training a student model, which
consists of good knowledge from all teachers' models. Therefore, our proposed
algorithm can effectively extract the knowledge of the regions' data
distribution (i.e., the regional aggregated models) to reduce the divergence
between clients' models when operating under the FL system with non-independent
identically distributed data. Extensive experiment results reveal that: (i) our
F2L method can significantly improve the overall FL efficiency in all global
distillations, and (ii) F2L rapidly achieves convergence as global distillation
stages occur instead of increasing on each communication cycle.Comment: 28 pages, 5 figures, 10 table
EFFECTS OF SUBSTITUENTS ON CH BOND DISSOCIATION ENTHALPIES OF ENT-KAURANE DITERPENOIDS: A DFT STUDY
C-H bond dissociation enthalpies (BDEs) of seven ent-kaurane diterpenoids extracted from Croton tonkinensis Gagnep. have been investigated by using density functional theory (DFT) method. The calculations were performed at the M05-2X/6-31+G(d) level of theory. Additionally, insight into the effects of different substituents including âNH2, âOH, âNO2, âSH, âCN, âCl, âCONH2, âCH-(CH3)2, âNHCOCH3, âOCOCH3 and âC2H5 on BDE have also been provided. The results showed that the BDE value of ent-16(S)-18-acetoxy-7b-hydroxykaur-15-one compound is lowest, being 83.5 kcal/mol. Among substituents binding at C16 position of this molecule, âNH2 has the most remarkable influence on the BDE (C-H) value. Indeed, the BDE of C16-H significantly decreases from 83.5 to 68.4 kcal/mol when replacing âCH3 group by âNH2 one at the C16 position. The obtained results may provide more information for organic synthesis of ent-kaurane based â novel antioxidant compounds
TETRAOXYGENATED XANTHONES FROM THE LATEX OF GARCINIA COWA
Seven tetraoxygenated xanthones, namely fuscaxanthone A,7-O-methylgarcinone E, cowagarcinone A, cowaxanthone, rubraxanthone, cowanin and cowanol, were isolated from the dichloromethane extract of the latex of Garcinia cowa_Roxb. ex Choisy. Their structures were elucidated on the basis of 1D, 2D NMR spectroscopic data and comparison with reported data
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