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      • KCI등재

        Analog active valve control design for non-linear semi-active resetable devices

        Geoffrey W. Rodgers,J. Geoffrey Chase,Sylvain Corman 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.5

        Semi-active devices use the building\'s own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

      • KCI등재

        Climate Change on Agriculture in 2050: A CGE Approach

        Geoffrey Musyoki Kitetu,고종환 한국무역연구원 2020 貿易 硏究 Vol.16 No.4

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

        Purpose Agriculture plays a very critical role in terms of global food security and provides livelihood to over 30 percent of the world population. This study investigates the economic impact of climate change on agriculture in 2050. Design/Methodology/Approach We employ the global, multi-sector computable general equilibrium (CGE) approach. Using the GTAP Version 10 database whose base year is 2014, we project the global economy to 2050 relative to 2014. The main focus is on the role of economic players’ adaptation response to climate change, and the possible changes in production quantities and market prices. We implement a baseline growth path simulation that does not account for climate change effects, and two counter-factual policy simulations, which account for the impacts of climate change. Findings Simulation results reveal that extreme climate change will negatively affect the market prices of agricultural commodities, private household consumption, trade balance, GDP, and welfare for most of the regions in this study. Further, developing economies are found to be affected more by climate change compared to developed nations. Research Implications The study suggests that climate change adaptation and mitigation policies be specific to every stage in the farm value chain (FVC) with more emphasis on production and market integration segments.

      • KCI등재
      • KCI등재
      • SCIESCOPUSKCI등재

        Review : NASH is an Infl ammatory Disorder: Pathogenic, Prognostic and Therapeutic Implications

        ( Geoffrey C. Farrell ),( Derrick Van Rooyen ),( Lay Gan ),( Shivrakumar Chitturi ) The Editorial Office of Gut and Liver 2012 Gut and Liver Vol.6 No.2

        While non-alcoholic fatty liver disease (NAFLD) is highly prevalent (15% to 45%) in modern societies, only 10% to 25% of cases develop hepatic fibrosis leading to cirrhosis, end-stage liver disease or hepatocellular carcinoma. Apart from pre-existing fibrosis, the strongest predictor of fibrotic progression in NAFLD is steatohepatitis or non-alcoholic steatohepatitis (NASH). The critical features other than steatosis are hepatocellular degeneration (ballooning, Mallory hyaline) and mixed infl ammatory cell infi ltration. While much is understood about the relationship of steatosis to metabolic factors (over-nutrition, insulin resistance, hyperglycemia, metabolic syndrome, hypoadiponectinemia), less is known about infl ammatory recruitment, despite its importance for the perpetuation of liver injury and fi brogenesis. In this review, we present evidence that liver infl ammation has prognostic signifi cance in NAFLD. We then consider the origins and components of liver infl ammation in NASH. Hepatocytes injured by toxic lipid molecules (lipotoxicity) play a central role in the recruitment of innate immunity involving Toll-like receptors (TLRs), Kupffer cells (KCs), lymphocytes and neutrophils and possibly infl ammasome. The key pro-infl ammatory signaling pathways in NASH are nuclear factor-kappa B (NF-κB) and c-Jun N-terminal kinase (JNK). The downstream effectors include adhesion molecules, chemokines, cytokines and the activation of cell death pathways leading to apoptosis. The upstream activators of NF-κB and JNK are more contentious and may depend on the experimental model used. TLRs are strong contenders. It remains possible that infl ammation in NASH originates outside the liver and in the gut microbiota that prime KC/TLR responses, infl amed adipose tissue and circulating infl ammatory cells. We briefl y review these mechanistic considerations and project their implications for the effective treatment of NASH. (Gut Liver 2012;6:149-171)

      • SCOPUSKCI등재

        Case Report : Acetazolamide for Cystoid Macular Oedema in Bietti Crystalline Retinal Dystrophy

        ( Geoffrey K Broadhead ),( Andrew A Chang ) 대한안과학회 2014 Korean Journal of Ophthalmology Vol.28 No.2

        Bietti crystalline retinal dystrophy is a rare, autosomal, recessively inherited disorder that is more common in patients of East Asian descent. This disease is characterised by the deposition of yellow crystals in the corneal limbus and retina, leading to the development of retinal and choroidal atrophy with resultant visual deterioration [1]. Optical coherence tomography (OCT) may show reflective deposits suggestive of crystalline deposits, and fundus fluorescein angiography (FFA) often demonstrates characteristic retinal pigment epithelium (RPE) atrophy [2]. This condition may also rarely be associated with choroidal neovascularisation (CNV) [3]. The prognosis for this disease is generally poor, Bietti crystalline retinal dystrophy is a rare, inherited disorder whose hallmark is the presence of retinal crystal deposits associated with later chorioretinal degeneration. This condition may rarely be complicated by the development of cystoid macular oedema leading to rapid visual decline. Currently, treatment options for this complication of Bietti dystrophy are limited and the visual prognosis is poor. Here, we present a case of cystoid macular oedema associated with Bietti dystrophy that was successfully diagnosed using multimodal imaging techniques including optical coherence tomography and fluorescein angiography. These modalities confirmed the diagnosis of macular oedema and excluded other possible causes of oedema such as choroidal neovascularisation. In this patient, cystoid macular oedema was resolved with oral acetazolamide therapy, a treatment that has not been previously reported in this context. Acetazolamide treatment resulted in oedema resolution and improvement in visual function, and can be considered a therapeutic option for other patients with Bietti dystrophy who develop cystoid macular oedema.

      • SSCISCOPUSKCI등재
      • KCI등재

        Macrophages in cardiac repair: Environmental cues and therapeutic strategies

        Geoffrey de Couto 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

        Mammals, in contrast to urodeles and teleost fish, lose the ability to regenerate their hearts soon after birth. Central to this regenerative response are cardiac macrophages, which comprise a heterogeneous population of cells with origins from the yolk sac, fetal liver, and bone marrow. These cardiac macrophages maintain residency in the myocardium through local proliferation and partial replacement over time by circulating monocytes. The intrinsic plasticity of cardiac macrophages in the adult heart promotes dynamic phenotypic changes in response to environmental cues, which may either protect against injury or promote maladaptive remodeling. Thus, therapeutic strategies promoting myocardial repair are warranted. Adult stromal cell-derived exosomes have shown therapeutic promise by skewing macrophages toward a cardioprotective phenotype. While several key exosomal non-coding RNA have been identified, additional factors responsible for cardiomyocyte proliferation remain to be elucidated. Here I review cardiac macrophages in development and following injury, unravel environmental cues modulating macrophage activation, and assess novel approaches for targeted delivery.

      • KCI등재
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