• Steel and Composite Structures
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• 제46권6호
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• pp.773-791
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• 2023

Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.

• Journal of Power Electronics
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• 제14권2호
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• pp.257-264
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• 2014

A novel converter-free AC LED driver that is highly resistant to the fluctuation of AC voltage is proposed in this study. By removing large passive components, such as the bulky capacitor and the large-value inductor, the integration of the driver circuit is enhanced while the driving current remains stable. The proposed circuit provides LED lamps with a driving current that can follow the sinusoid waveform to obtain a very high power factor (PF) and low total harmonic distortion (THD). The LED input current produced by this driving current is insensitive to fluctuations in the AC voltage. Users will thus not feel that LED lamps are flashing during the fluctuation. Experiment results indicate that the proposed system can obtain PF of 0.999 and THD as low as 3.3% for a five-string 6 W LED load under 220 V at 50 Hz.

• Journal of Power Electronics
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• 제16권2호
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• pp.717-730
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• 2016

The harmonic components of grid voltage result in oscillations of the calculated phase obtained via phase synchronization. This affects the security and stability of grid-connected converters. Moving average filter, delayed signal cancellation and their related harmonic elimination algorithms are major methods for such issues. However, all of the existing methods have their limitations in dealing with multiple harmonics issues. Furthermore, few studies have focused on a comparison and evaluation of these algorithms to achieve optimal algorithm selections in specific applications. In this paper, these algorithms are quantitatively analyzed based on the derived mathematical models. Moreover, an enhanced moving average filter and enhanced delayed signal cancellation algorithms, which are applicable for eliminating a group of selective harmonics with only one calculation block, are proposed. On this basis, both a comprehensive comparison and a quantitative evaluation of all of the aforementioned algorithms are made from several aspects, including response speed, required data storage size, sensitivity to sampling frequency, and elimination of random noise and harmonics. With the conclusions derived in this paper, better overall performance in terms of harmonic elimination can be achieved. In addition, experimental results under different conditions demonstrate the validity of this study.

• 한국미생물·생명공학회지
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• 제41권1호
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• pp.52-59
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• 2013

The nutritional requirements for the maximum production of lipopeptides by Bacillus subtilis N7 (B. subtilis N7) were investigated and optimized using response surface methodology (RSM) under shake flask fermentation. A one-factor-at-a-time experimental setup was used to screen carbon and nitrogen sources. A Plackett-Burman design (PBD) was employed to screen the most critical variables for lipopeptides production amongst ten nutritional elements. The central composite experimental design (CCD) was finally adopted to elucidate the composition of the fermentation medium. Statistical analyses (analysis of variance, ANOVA) of the results showed that KCl, $MnSO_4$ and $FeSO_4{\cdot}6H_2O$ were important components and that their interactions were strong. Lipopeptide production was predicted to reach 709.87 mg/L after a 60 h incubation using an optimum fermentation medium composed of glucose 7.5 g/L, peanut oil 1.25 g/L, $MgSO_4$ 0.37 g/L, $KH_2PO_4$ 0.75 g/L, monosodium glutamate 6.75 g/L, yeast extract and $NH_4Cl$ (5:3 w/w) 10 g/L, KCl 0.16 g/L, $FeSO_4{\cdot}6H_2O$ 0.24 mg/L, $MnSO_4$ 0.76 mg/L, and an initial pH of 7.0. Lipopeptide production ($706.57{\pm}3.70$ mg/L) in the optimized medium confirmed the validity of the predicted model.

• Geomechanics and Engineering
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• 제11권5호
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• pp.607-624
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• 2016

Rockburst is becoming more serious in Chinese coal mine. One of the effective methods to control rockburst is blasting. In the paper, we monitored and analyzed the blasting waves at different blast center distances by the Hilbert-Huang transform (HHT) in a coal mine. Results show that with the increase of blast center distance, the main frequency and amplitude of blasting waves show the decreasing trend. The attenuation of blasting waves is slower in the near blast field (10-75 m), compared with the far blast field (75-230 m). Besides, the frequency superposition phenomenon aggravates in the far field. A majority of the blasting waves energy at different blast center distances is concentrated around the IMF components 1-3. The instantaneous energy peak shows attenuation trend with the blast center distance increase, there are two obvious energy peaks in the near blast field (10-75 m), the energy spectrum appears "fat", and the total energy is greater. By contrast, there is only an energy peak in the far blast field, the energy spectrum is "thin", and the total energy is lesser. The HHT three dimensional spectrum shows that the wave energy accumulates in the time and frequency with the increasing of blast center distance.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2156-2162
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• 2012

Many literatures focus on the biological relevance and the identification of biomarkers for disease activity assessment while less attention has been paid to the development of standard procedures for sample preparation and storage based on liquid chromatography technique. The influencing factors including protein precipitation, storage temperature, storage time, and reconstitution by ultra pure water were analyzed employing HPLC-DAD. The effects were investigated from five participants over three months by principal components analysis (PCA) and the values of percent changes (PC). The samples with protein precipitation might slow the rate of bacterial enzymatic conversion. After protein precipitation, the average PC of urine samples ($0.136{\pm}0.013$, n = 5) is relatively less than that of the serum samples ($0.173{\pm}0.026$, n = 5) for three months. Minimal effects on metabolic profiles of serum and urine (PC < 0.15) are reasonable for metabolomic studies after protein precipitation and storage at $-20^{\circ}C$ for two months.

• Steel and Composite Structures
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• 제29권4호
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• pp.545-555
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• 2018

This study aimed to investigate the flexural behavior of precast concrete (PC) wall - steel shoe composite assemblies with various dry connection details at mid-span. Flexural tests were performed for five scenarios. Test parameters included the width of test specimens, arrangement of steel shoe connectors, and use of structural adhesive or waterproof tape at the mid-span joint. The test results showed that the PC wall - steel shoe composite assemblies joined at mid-span showed flexural damage patterns combined with rotational deformation, and the structural performance was satisfactory regardless of the arrangement of steel shoe connectors. Considering the two deformation components (flexural deformation by bending and rotational deformation due to joint opening), a theoretical model was proposed to analyze flexural strength and joint opening, and the simple model gave good predictions with acceptable accuracy.

• 정보보호학회논문지
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• 제18권5호
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• pp.49-57
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• 2008

안전한 홈네트워크 서비스를 제공하는데 있어서 사용자 인증 및 키교환은 아주 중요한 구성요소이다. TTA는 사용자 인증과 키전송 표준으로 EEAP-PW를 채택하고 있지만 이 프로토콜은 전방향 안전성을 제공하지 못하는 것을 포함한 몇 가지 문제를 가지고 있다. 본 논문에서는 먼저 EEAP-PW 프로토콜의 문제점을 분석하고 이를 효율적으로 해결할 수 있는 속성기반의 인증된 키교환 프로토콜(EEAP-AK)을 제안한다. 제안한 프로토콜은 사용자의 속성에 기반한 인증과 키 교환 후 사용자 속성에 따라 홈 네트워크 서비스의 접근성을 차별화 시킴으로 보안의 다양한 레벨을 제공한다. 본 논문에서 제안하는 프로토콜은 EEAP-PW의 문제점을 효율적으로 해결할 수 있어 EEAP-AK를 통한 보다 안전한 홈네트워크 서비스를 제공할 수 있을 것으로 기대된다.

• Journal of Microbiology and Biotechnology
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• 제32권12호
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• pp.1622-1631
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• 2022

Carotenoids, which are natural pigments found abundantly in wide-ranging species, have diverse functions and high industrial potential. The carotenoid biosynthesis pathway is very complex and has multiple branches, while the accumulation of certain metabolites often affects other metabolites in this pathway. The DsLCYB gene that encodes lycopene cyclase was selected in this study to evaluate β-carotene production and the accumulation of β-carotene in the alga Dunaliella salina. Compared with the wild type, the transgenic algal species overexpressed the DsLCYB gene, resulting in a significant enhancement of the total carotenoid content, with the total amount reaching 8.46 mg/g for an increase of up to 1.26-fold. Interestingly, the production of α-carotene in the transformant was not significantly reduced. This result indicated that the regulation of DsLCYB on the metabolic flux distribution of carotenoid biosynthesis is directional. Moreover, the effects of different light-quality conditions on β-carotene production in D. salina strains were investigated. The results showed that the carotenoid components of β-carotene and β-cryptoxanthin were 1.8-fold and 1.23-fold higher than that in the wild type under red light stress, respectively. This suggests that the accumulation of β-carotene under red light conditions is potentially more profitable.

• Parasites, Hosts and Diseases
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• 제61권1호
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• pp.42-52
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• 2023

The genus Babesia includes parasites that can induce human and animal babesiosis, which are common in tropical and subtropical regions of the world. The gut microbiota has not been examined in hamsters infected by Babesia duncani. Red blood cells infected with B. duncani were injected into hamsters through intraperitoneal route. To evaluate the changes in gut microbiota, DNAs were extracted from small intestinal contents, acquired from hamsters during disease development. Then, the V4 region of the 16S rRNA gene of bacteria was sequenced using the Illumina sequencing platform. Gut microbiota alternation and composition were assessed according to the sequencing data, which were clustered with >97.0% sequence similarity to create amplicon sequence variants (ASVs). Bacteroidetes and Firmicutes were made up of the major components of the gut microbiota in all samples. The abundance of Bacteroidetes elevated after B. duncani infection than the B. duncani-free group, while Firmicutes and Desulfobacterota declined. Alpha diversity analysis demonstrated that the shown ASVs were substantially decreased in the highest parasitemia group than B. duncani-free and lower parasitemia groups. Potential biomarkers were discovered by Linear discriminant analysis Effect Size (LEfSe) analysis, which demonstrated that several bacterial families (including Muribaculaceae, Desulfovibrionaceae, Oscillospiraceae, Helicobacteraceae, Clostridia UGG014, Desulfovibrionaceae, and Lachnospiraceae) were potential biomarkers in B. duncani-infected hamsters. This research demonstrated that B. duncani infectious can modify the gut microbiota of hamsters.