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Analysis and Verification of the Stability for PV Series-Connected Power Optimizer System
Yutai Fu,Jizhi Qi,Yonghao Li,Xinghua Zhang,Min Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Photovoltaic (PV) energy generation gets more and more attention in the last decades. Among many structures of PV system, series-connected power optimizer (SCPO) system is regarded as a promising one. However, the cross-coupling effect introduced by the series-connected structure cannot be avoided, which would weaken the stability of the system, resulting in failure of operation of the system. Therefore, it is significant to analysis the stability of the series-connected system and suppress the effect by improving the closed-loop control strategy and compensation design. In this paper, the small-signal ac model consisting of three optimizers is derived and the criterions of stability and compensation design are proposed. Computer simulation and hardware experiment are used to verify the validity of the proposed theories.
Dangol, Manita,Kim, Suyong,Li, Cheng Guo,Fakhraei Lahiji, Shayan,Jang, Mingyu,Ma, Yonghao,Huh, Inyoung,Jung, Hyungil Elsevier 2017 Journal of controlled release Vol.265 No.-
<P><B>Abstract</B></P> <P>Natural products such as caffeine have been found to be effective in reducing body weight through lipolysis. Here, we report the successful loading of caffeine onto dissolving microneedle following inhibition of its crystal growth by hyaluronic acid (HA), the matrix material of the dissolving microneedle (DMN). Further, the anti-obesity activity of caffeine was evaluated in high-fat diet-induced obese C57BL/6J mice. After 6weeks of caffeine loaded dissolving microneedle patch (CMP) administration, lipolysis improved significantly as shown by leptin and adiponectin activity, which resulted in considerable weight loss of about 12.8±0.75% in high-fat diet-induced obese mice. Comparison of the levels of triglyceride, total cholesterol, high-density lipoprotein (HDL)-cholesterol, and low-density lipoprotein (LDL)-cholesterol after CMP administration with the initial levels in obese mice indicated significant anti-obesity activity of CMP. These findings suggested that a novel CMP with an increased amount of caffeine loaded onto DMN has therapeutic activity against obesity.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Fakhraei Lahiji, Shayan,Seo, Seol Hwa,Kim, Suyong,Dangol, Manita,Shim, Jiyong,Li, Cheng Guo,Ma, Yonghao,Lee, Chisong,Kang, Geonwoo,Yang, Huisuk,Choi, Kang-Yell,Jung, Hyungil Elsevier 2018 Biomaterials Vol.167 No.-
<P><B>Abstract</B></P> <P>The interest in alternative material systems and delivery methods for treatment of androgenetic alopecia has been increasing in the recent decades. Topical application of valproic acid (VPA), an FDA-approved anticonvulsant drug, has been shown to effectively stimulate hair follicle (HF) regrowth by upregulating Wnt/β-catenin, a key pathway involved in initiation of HF development. Moreover, a majority of studies have suggested that cutaneous wound re-epithelialization is capable of inducing HF through Wnt/β-catenin pathway. Here, we report fabrication and evaluation of a novel VPA-encapsulating dissolving microneedle (DMN-VPA) that creates minimally invasive dermal micro-wounds upon application, significantly improving the VPA delivery efficiency. DMN-VPA not only delivers encapsulated VPA with higher accuracy than topical application, it also stimulates wound re-epithelialization signals involved in HF regrowth. Through a series of <I>in vivo</I> studies, we show that micro-wounding-mediated implantation of DMN-VPA upregulates expression of Wnt/β-catenin pathway, alkaline phosphatase, proliferating cell nuclear antigen, loricrin and HF stem cell markers, including keratin 15, and CD34 more effectively than topical application.</P>
A novel and effective approach to enhance the interfacial interactions of meta-aramid fibers
Hui Zhang,Xiaoyun Du,Jiawei Liu,YunHong Bai,Jingyi Nie,Jiaojun Tan,Zhibin He,Meiyun Zhang,Jinbao Li,Yonghao Ni 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.120 No.-
Meta-aramid paper exhibits some unique properties, including high temperature resistance, electricalinsulation. However, due to the inherent chemical inertness of aramid fibers, the interfacial bondingbetween fibers is weak, which negatively affect the properties of aramid paper. Herein, we report a simple,effective and scalable process for substantially improving the interfacial bonding between aramidfibers, thus, mechanical and insulating properties of the meta-aramid composite paper, and it wasachieved by surface coating of aramid paper with meta-aramid stock solution that contains N, N dimethylacetamide(DMAc)-CaCl2 and high molecular weight poly (m-phenylene isophthalamide) polymers. Results show that the tensile strength, modulus, internal bond strength and tearing index of the resultantall-PMIA paper increased by 83 %, 58 %, 173 % and 89 %, respectively, in comparison with those of the control. The breakdown strength of the improved aramid paper is 190 % higher than that of the control paper,attaining 26.46 KV/mm. This work provides a simple, economical, efficient, and scalable method toimprove the overall performance of meta-aramid paper, which has great potential to be implementedat the industrial scale.
Kim, Suyong,Dangol, Manita,Kang, Geonwoo,Lahiji, Shayan F.,Yang, Huisuk,Jang, Mingyu,Ma, Yonghao,Li, Chengguo,Lee, Sang Gon,Kim, Chang Hyun,Choi, Young Wook,Kim, So Jeong,Ryu, Ja Hyun,Baek, Ji Hwoon,K American Chemical Society 2017 Molecular Pharmaceutics Vol.14 No.6
<P>Dissolving microneedle (DMN), a transdermal drug delivery system in which drugs are encapsulated in a biodegradable polymeric microstructure, is designed to dissolve after skin penetration and release the encapsulated drugs into the body. However, because of limited loading capacity of drugs within microsized structures, only a small dosage can be delivered, which is often insufficient for patients. We propose a novel DMN application that combines topical and DMN application simultaneously to improve skin permeation efficiency. Drugs in pretreated topical formulation and encapsulated drugs in DMN patch are delivered into the skin through microchannels created by DMN application, thus greatly increasing the delivered dose. We used 4-n-butylresorcinol to treat human hyper pigmentation and found that sequential application of serum formulation and DMNs was successful. In skin distribution experiments using Alexa Fluor 488 and 568 dyes as model drugs, we confirmed that the pretreated serum formulation was delivered into the skin through microchannels created by the DMNs. In vitro skin permeation and retention experiments confirmed that this novel combined application delivered more 4-n-butylresorcinol into the skin than traditional DMN-only and serum-only applications. Moreover, this combined application showed a higher efficacy in reducing patients' melanin index and hyperpigmented regions compared with the serum-only application. As combined application of DMNs on serum-treated skin can overcome both dose limitations and safety concerns, this novel approach can advance developments in transdermal drug delivery.</P>