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The origin, evolution, and application of the megapolitan area concept
Robert E. Lang,임재원,Karen A. Danielsen 서울시립대학교 도시과학연구원 2020 도시과학국제저널 Vol.24 No.1
The article explores the origin and evolution of the ‘megapolitan concept', the idea of a super-sized region that began in 1961 in Jean Gottmann's ‘megalopolis,' which he developed to explain large-scale urbanization in the Northeastern U.S. Jerome Picard, a researcher at the Urban Land Institute took up the megalopolis idea in 1967 and applied it to the entire U.S. and projected large-scale urban growth to 2000. The Regional Plan Association (RPA) also applied the megalopolis concept to The Second Regional Plan for New York in 1968. Lang in 2000s, then working with his colleagues at Virginia Tech developed the megapolitan concept and definition-in part to differential the concept from work being done by the University of Pennsylvania for RPA. Lang defined ‘megapolitan clusters’ as multiple megapolitan areas that are networked either by commuting, logistics, or dense air links, but where there is no more than three times the distance used to define a Megapolitan Area between anchor metropolitan areas at their furthest distance. The recent evolution of megapolitan area and megapolitan cluster concepts by Lang and the colleagues is applied to a series of projects, including ‘Sun Corridor’ in 2006 (Phoenix-Tucson) and the Southwest Triangle (SoCal-Sun Corridor-Las Vegas) in 2014. The article ends with the future application of megapolitan area concept in the rapidly growing Southwest Triangle megapolitan cluster.
( Lang Victoria Lee ),( Sang Gu ) 한국수학교육학회 2014 뉴스레터 Vol.30 No.5
The notion of the reanimated dead (i.e. "zombies") has a strong historical basis that has fascinated the general public for centuries. The zombie still remains a popular figure in entertainment media; specifically, in video games. Expanding upon the well-known S.I.R. epidemiological model. we first examine basic models for zombie infection first introduced by Munz, Hudea, Imad & Smith? (2009). Specifically, we modify these models to be visualized online via Sage, an open-source mathematics software based in the Python programming language, that allows for direct user interaction. We then focus on viewing mathematically "realistic" population trajectories for the different classes of zombies from Left 4 Dead<http://www.14d.com/blog/> Valve Corporation`` s immensely popular video game series that revolves around human players surviving a pandemic of zombie infection. The respective strengths, weaknesses, and dynamics of each zombie class are mathematically established, and all outcomes are numerically realized with online Sage tools. These models are available for viewing, manipulation, and use in a mobile environment at <http://matrix. skku.ac.kr/2014-Zombie-Model>and, thus, can serve as an effective and exciting academic tool for the interested student of any college-level Ordinary Differential Equations course.
Interpretations for China’s Weak Role in Managing the DPRK Nuclear Crisis
LANG KUN,이철호 21세기정치학회 2019 21세기 정치학회보 Vol.29 No.2
East Asian regional stability requires a peaceful solution to the DPRK nuclear crisis. Even though the ultimate rescue of this issue belongs to the US-DPRK rapprochement, Chin’s role in the DPRK denuclearization process turns out non-significant. This paper aims to interpret the reasons for China’s powerlessness in two dimensions: the Chinese-culture-born ‘all-under-heaven philosophy’ that influences Chinese diplomacy has not been provided China a Western-acceptable international relations theory to deal with the DPRK nuclear crisis; China’s changing strategy toward DPRK reduced the trust from relevant countries, which led to China’s voicelessness. Meanwhile, China’s efforts and contributions to improving the DPRK nuclear issue shouldn’t be ignored. As long as the pivot of the tribute system as a traditional peace management mechanism is ‘a rich China’ rather than ‘a forceful China’, the so-called ‘Chinese School’ should focus the efforts on economic issues that would benefit the relevant countries. In the same context, the stability of Korean peninsula should start from the exchange activities in the ‘low politics’ areas which would consolidate the public support for bilateral ties.
N-Step Sliding Recursion Formula of Variance and Its Implementation
Lang Yu,Gang He,Ahmad Khwaja Mutahir 한국정보처리학회 2020 Journal of information processing systems Vol.16 No.4
The degree of dispersion of a random variable can be described by the variance, which reflects the distance of the random variable from its mean. However, the time complexity of the traditional variance calculation algorithm is O(n), which results from full calculation of all samples. When the number of samples increases oron the occasion of high speed signal processing, algorithms with O(n) time complexity will cost huge amount of time and that may results in performance degradation of the whole system. A novel multistep recursive algorithm for variance calculation of the timevarying data series with O(1) time complexity (constant time) is proposed in this paper. Numerical simulation and experiments of the algorithm is presented and the results demonstrate that the proposed multistep recursive algorithm can effectively decrease computing time and hence significantly improve the variance calculation efficiency for timevarying data, which demonstrates the potential value for timeconsumption data analysis or high speed signal processing.
Lang Zheng,Weijun Zhen 한국고분자학회 2018 폴리머 Vol.42 No.4
An improved Hummers method was used to prepare graphene oxide (GO). Then, the orthogonal experiment design methods were used to select the optimum conditions of preparation for graphene oxide-polymethyl methacrylate (GO-PMMA) via activators regenerated by electron transfer for atom transfer radical polymerization (AGET-ATRP). The optimum preparation conditions were determined by orthogonal tests. Furthermore, poly(lactic acid) (PLA)/GO-PMMA nanocomposites were prepared by melt blending to improve the comprehensive performance of PLA. Analysis results indicated that methyl methacrylate (MMA) was successfully grafted onto GO, and the addition of 0.3 wt% of GO-PMMA increased the tensile strength, elongation at break, and impact strength of PLA/GO-PMMA nanocomposites by 7.82, 40.66, and 50.62%, respectively, compared with PLA. Moreover, GO-PMMA eliminated the cold crystallization of PLA matrix and improved the crystallinity of PLA by 27.55%. In all, this study provided an effective and feasible method for improving the comprehensive performance of PLA.
Co‑doped amorphous MoSx for efficient hydrogen evolution reaction in acid condition
Lang Gan,Jincheng Liu,Yanjie Ren,Zhongyi Xiong,Kang Chen 한국탄소학회 2023 Carbon Letters Vol.33 No.5
Amorphous molybdenum sulfide ( MoSx) has been regarded as a promising hydrogen evolution reaction (HER) catalyst due to its mild preparation conditions and low-cost precursor materials. In this work, we report a simple strategy combining the growth of amorphous MoSx on the surface of metal organic frameworks (ZIF-67) and annealing treatment to prepare Co-doped MoSx nanopolyhedrons (denoted as CoMoSx NPs). The CoMoSx NPs exhibit excellent HER activity in acid condition with an overpotential of 188 mV at a current density of 10 mA cm? 2 (η10), and a relatively stable overpotential after 2000 cyclic voltammetry (CV) cycles testing. The excellent HER performance of the CoMoSx NPs can be attributed to the doping of Co element adjust the electronic structure and increase the conductivity of catalyst, and the nanopolyhedrons structure which can expose more active sites for HER electrocatalytic. This study offers a low-cost and simple strategy to prepare high-activity HER catalyst, which holds great promises in developing advanced electrocatalysts for energy storage.
Opioid-induced constipation: a narrative review of therapeutic options in clinical management
Lang-Illievich, Kordula,Bornemann-Cimenti, Helmar The Korean Pain Society 2019 The Korean Journal of Pain Vol.32 No.2
Pain therapy often entails gastrointestinal adverse events. While opioids are effective drugs for pain relief, the incidence of opioid-induced constipation (OIC) varies greatly from 15% to as high as 81%. This can lead to a significant impairment in quality of life, often resulting in discontinuation of opioid therapy. In this regard, a good doctor-patient relationship is especially pivotal when initiating opioid therapy. In addition to a detailed history of bowel habits, patient education regarding the possible gastrointestinal side effects of the drugs is crucial. In addition, the bowel function must be regularly evaluated for the entire duration of treatment with opioids. Furthermore, if the patient has preexisting constipation that is well under control, continuation of that treatment is important. In the absence of such history, general recommendations should include sufficient fluid intake, physical activity, and regular intake of dietary fiber. In patients of OIC with ongoing opioid therapy, the necessity of opioid use should be critically reevaluated in terms of an with acceptable quality of life, particularly in cases of non-cancer pain. If opioids must be continued, lowering the dose may help, as well as changing the type of opioid. If these measures do not suffice, the next step for persistent OIC is the administration of laxatives. If these are ineffective as well, treatment with peripherally active ${\mu}$-opioid receptor antagonists should be considered. Enemas and irrigation are emergency measures, often used as a last resort.
Lang Zhou,Jiantao Kong,Ying-ping Zhuang,Ju Chu,Si-Liang Zhang,Mei-Jin Guo 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1
Bone marrow mesenchymal stem cells (bmMSCs)have recently gained attention as a useful resource in the fields of regenerative medicine and tissue engineering. However, the number of bmMSCs obtained from available donors is very low. Here we developed a culture strategy for in vitro expansion of bmMSCs in a 1.5 L stirred bioreactor with microcarrier beads. First, the microcarriers (Cytodex 3) were equilibrated in culture medium containing 3% fetal bovine serum (FBS) for at least 30 min prior to cell addition. After inoculation, the FBS concentration of the medium was maintained at 3% (v/v) in the first 24 h and thereafter maintained at 1% (v/v) and a developed feeding regimen was applied over 5 days. The maximum cell density of 2.6 × 106 cells/mL was achieved at day 5,corresponding to a 10.4 ± 0.8 fold increases in total cell number. Among the harvested cells, 98.95% expressed CD29and 84.48% expressed CD90, suggesting that the majority of expanded bmMSCs still retained their differentiation potential. Therefore, the developed microcarrier-based stirred bioreactor culture system is an effective method to generate significant numbers of bmMSCs for potential applications and research studies.
Recovery of mortar-aggregate interface of fire-damaged concrete after post-fire curing
Lang Li,Hong Zhang,Jiangfeng Dong,Hongen Zhang,Pu Jia,Qingyuan Wang,Yongjie Liu 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.3
In order to investigate the strength recovery of fire-damaged concrete after post-fire curing, concrete specimens were heating at 2°C/min or 5°C/min to 400, 600 and 800°C, and these exposed specimens were soaked in the water for 24 hours and following by 29-day post-fire curing. The compressive strength and split tensile strength of the high-temperature-exposed specimens before and after post-fire curing were tested. The proportion of split aggregate in the split surfaces was analyzed to evaluate the mortar-aggregate interfacial strength. After the post-fire curing process, the split tensile strength of specimens exposed to all temperatures was recovered significantly, while the recovery of compressive strength was only obvious within the specimens exposed to 600°C. The tensile strength is more sensitive to the mortar-aggregate interfacial cracks, which caused that the split tensile strength decreased more after high-temperature exposure and recovery more after post-fire curing than the compressive strength. The mortar-aggregate interfacial strength also showed remarkable recovery after post-fire curing, and it contributed to the recovery of split tensile strength.
Lang Huang,Xu Yang,Bin Zhang,Liang Qiao,Hongchang Li,Mofan Tian 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The modular multilevel matrix converter (M3C) applied to a low frequency alternating current (LFAC) transmission system is investigated. Due to the complexity and tight coupling of the converter, a novel hierarchical model predictive control (MPC) scheme with a cascaded structure of power control, capacitor voltage averaging and balancing control for M3C is proposed. The terminal behavioral model of M3C is derived out and the fast separated space-vectors approximation method is realized. The proposed scheme clearly achieves the system-level multi-objective control without the empirical procedure of the weighting factor design and significantly reduces the computational cost. This is the first time to apply the MPC to a converter in a hierarchical structure. Simulation results of a 7-level M3C are provided to illustrate the system’s performance.