• East Asian Economic Review
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• 제20권4호
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• pp.493-517
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• 2016

This paper examines the persistent properties of 12 sectoral relative prices between Korea and Japan obtained following the Classification of Individual Consumption according to Purpose (COICOP) over the period of 1985-2016. Applying a new econometric method developed by Pesaran which controls for the cross-section dependence in a panel, we are not able to reject the hypothesis that the sectoral real exchange rates contain a common stochastic trend. On the other hand, the well-known panel unit root tests such as the IPS and LLC tests widely used by previous studies strongly reject the unit root hypothesis. Since the error term of the regression for our panel exhibits significant cross-section dependence, these opposite results justify that the use of the new econometric method is appropriate.

• 대한수학회지
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• 제56권3호
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• pp.825-855
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• 2019

We establish the existence of $C^1$ stable invariant manifolds for differential equations $u^{\prime}=A(t)u+f(t,u,{\lambda})$ obtained from sufficiently small $C^1$ perturbations of a nonuniform exponential dichotomy. Since any linear equation with nonzero Lyapunov exponents has a nonuniform exponential dichotomy, this is a very general assumption. We also establish the $C^1$ dependence of the stable manifolds on the parameter ${\lambda}$. We emphasize that our results are optimal, in the sense that the invariant manifolds are as regular as the vector field. We use the fiber contraction principle to establish the smoothness of the invariant manifolds. In addition, we can also consider linear perturbations, and thus our results can be readily applied to the robustness problem of nonuniform exponential dichotomies.

• Journal of Preventive Medicine and Public Health
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• 제51권1호
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• pp.1-5
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• 2018

Smokers keep smoking despite knowing that tobacco claims many lives, including their own and others'. What makes it hard for them to quit smoking nonetheless? Tobacco companies insist that smokers choose to smoke, according to their right to self-determination. Moreover, they insist that with motivation and willpower to quit smoking, smokers can easily stop smoking. Against this backdrop, this paper aims to discuss the addictive disease called tobacco use disorder, with an assessment of the addictiveness of tobacco and the reasons why smoking cessation is challenging, based on neuroscientific research. Nicotine that enters the body via smoking is rapidly transmitted to the central nervous system and causes various effects, including an arousal response. The changes in the nicotine receptors in the brain due to continuous smoking lead to addiction symptoms such as tolerance, craving, and withdrawal. Compared with other addictive substances, including alcohol and opioids, tobacco is more likely to cause dependence in smokers, and smokers are less likely to recover from their dependence. Moreover, the thinning of the cerebral cortex and the decrease in cognitive functions that occur with aging accelerate with smoking. Such changes occur in the structure and functions of the brain in proportion to the amount and period of smoking. In particular, abnormalities in the neural circuits that control cognition and decision-making cause loss of the ability to exert self-control and autonomy. This initiates nicotine dependence and the continuation of addictive behaviors. Therefore, smoking is considered to be a behavior that is repeated due to dependence on an addictive substance, nicotine, instead of one's choice by free will.

• 통상정보연구
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• 제16권2호
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• pp.199-218
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• 2014

본 연구는 1995년부터 2010년까지 국가 에너지통계의 에너지소비, 생산, 수출 입 등 실적자료를 바탕으로 우리나라의 에너지경제효율을 분석하였다. 에너지 수출 입과 에너지 생산 자료를 통해 에너지원단위, 에너지순수입의존도, 에너지자립도 I, II 를 산출하고 국가경제규모와 비교분석을 통해 우리날 에너지경제 수준을 살펴보고 시사점을 제시하는데 목적이 있다. 에너지원단위 지표를 통한 에너지효율수준 분석이 주로 이루어졌다면, 본 연구는 에너지순수입의존도와 에너지자립도를 통해 국가 에너지 수출 입구조와 에너지생산수준을 추가적으로 살펴볼 수 있는 장점이 있다고 하겠다. 연구 결론으로 우리나라는 에너지경제효율 수준이 상당히 낮은 수준으로 국가적 정책 차원의 에너지효율개선의 필요성을 제기한다.

• 천문학회보
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• 제45권1호
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• pp.65.3-66
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• 2020

We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)-density relation over cosmic time. We construct several samples of galaxies at different redshifts from z=2.0 to z=0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z=0.0, but its dependence on local density becomes weaker with redshift. At z≳1.0, the SFR of galaxies increases with local density (reversal of the SFR-density relation), and its dependence becomes stronger with redshift. This change of SFR-density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z~1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z=0.0-2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR-density relation at z≳1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe.

• 한국콘텐츠학회논문지
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• 제22권10호
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• pp.827-839
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• 2022

스마트폰중독에 가장 취약한 집단으로 알려져 있는 초기청소년의 스마트폰의존에 대한 심각성이 증가하고 있다. 본 연구에서는 초기청소년의 스마트폰 의존도 영향요인을 초등학생과 중학생을 구분하여 분석하고자 하였다. 연구목적을 위해 2018년 한국아동청소년패널조사의 1차 조사 자료를 활용하였으며 초등학교 4학년 2,607명과 중학교 1학년 2,590명이 최종적으로 분석에 활용되었다. 초등학생과 중학생의 스마트폰의존도에 공통적으로 영향을 미치는 요인은 성별, 자아존중감, 공격성, 부모와 함께 보내는 시간, 부정적 양육태도로 나타났다. 한편 지역(규모), 경제수준, 건강상태, 학교생활만족도, 교사관계는 초등학생의 스마트폰의존도에는 유의하였으나 중학생에게는 유의하지 않았다. 중학생에게서는 부모의 긍정적 양육태도가 유의하였다. 분석결과를 바탕으로 초기청소년들의 올바른 스마트폰 사용을 장려하기 위한 정책수립 및 사회서비스제공에 대한 함의를 도출하였다.

• 한국문헌정보학회지
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• 제48권1호
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• pp.329-343
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• 2014

본 연구는 대학도서관의 이용행태와 서비스의 혜택에 대한 인식이 이용자의 진술을 통해 가치가 도출되는 CVM을 적용해 측정한 도서관 서비스의 가치에 미치는 영향을 파악하고자 하였다. 이용행태의 변인은 도서관 방문 이용, 도서관 웹사이트 이용, 소속도서관 의존도이며, 혜택인식의 변인은 수업 및 강의, 논문 및 연구, 취업 및 외부활동에 대한 혜택의 만족도이다. 대학도서관 서비스는 도서대출, 해외 및 국내 논문, 참고서비스, 이용교육, 열람실 이용 서비스로 나누어 WTP를 측정하였다. 이용행태에 관한 가설 검증 결과 도서관의 방문 이용이 도서대출, 해외 논문 이용, 참고서비스, 이용교육에 대한 WTP에 영향을 미치며, 소속도서관의 의존도가 대출과 이용교육에 영향을 미치는 것으로 나타났다. 대학도서관이 제공하는 혜택에 대한 인식에 관한 가설 검증에서는 수업 및 강의의 혜택에 대한 만족도가 열람실 이용에 대한 WTP에 영향을 미치는 것으로 나타났다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권10호
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• pp.4973-4977
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• 2012

Introduction: Tobacco use is a global health care problem. Repetitive exposure to nicotine produces neuroadaptation resulting in nicotine dependence. Smoking is associated with a range of diseases, causing high levels of morbidity and mortality and is one of the leading causes of preventable deaths, with more than 4.6 million smokers worldwide dying each year from smoking related illnesses. Stopping smoking has major health benefits. Quitting at any age provides both short and long term benefits. Materials and methods: 45 patients attending the outpatient department at the Oxford Dental College, Bangalore, were randomly allocated to three groups of interventions namely placebo, counseling and nicotine replacement therapy (NRT). Initially each one was assessed for carbon monoxide levels using a breath analyser (pico smokerlyser bedfont UK). They were followed up for six months and the carbon monoxide levels were again assessed using the same instrument. The paired t test was used to compare the results before and after the intervention. Results: The scores before the initiation of intervention and after treatment were compared and all three interventions were found to be statistically significant after six months. It was noticed that patients with very low or low dependence followed by high dependence had good response in the placebo group (68% and 47.6% respectively), in the counseling group maximum response was seen in the medium followed by the very low group (61% and 59% respectively), and maximum response was seen in very high followed by the very low group with NRT (78.7% and 60.5% respectively). Conclusion: The inference that can be drawn from the present study is that non-invasive, non pharmacological methods like placebo and counseling are effective in low to medium groups, and NRT is effective with higher nicotine dependence.

• Biomolecules & Therapeutics
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• 제19권1호
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• pp.45-51
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• 2011

These experiments were designed to use typical makers from behaviors and molecular basis in addicted animals of morphine and cocaine. Morphine has been widely abused with a high physical dependence liability. Morphine withdrawal activates the intracellular cAMP signaling pathway and further leads to changes in the expression of the cAMP response element binding protein (CREB), which may be important to the development and expression of morphine dependence. From these experiments, repeated morphine (10 mg/kg, twice per day for 7 days) developed physical dependence. Withdrawal signs were precipitated by naloxone and also increased the expression of the CREB. In addition, repeated exposure of cocaine (15 mg/kg) to mice develops locomotor sensitization and produced lasting behavioral sensitivity. Cocaine- and amphetamine-regulated transcript peptide (CART) peptide was up-regulated by repeated administration of cocaine in the striatum. Therefore, repeated morphine induced the development of physical dependence and increased pCREB. In addition, repeated cocaine induced locomotor sensitization and over-expressed CART peptide. In conclusion, the development of physical dependence and pCREB for morphine, and locomotor sensitization and CART peptide over-expression for cocaine would be useful markers to predict the abuse potential of opioid analgesics and pychostimulant drugs in animals, respectively.

• Archives of Pharmacal Research
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• 제29권8호
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• pp.677-684
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• 2006

Morphine has been used widely on the treatment of many types of chronic pain. However the development of tolerance to and dependence on morphine by repeat application is a major problem in pain therapy. The purpose of the present study was to investigate whether combined administration of nalbuphine with morphine affects the development of tolerance to and dependence on morphine. We hypothesize that the use of nalbuphine, ${\kappa}-agonist$ may prove to be useful adjunct therapy to prevent morphine-induced undesirable effects in the management of some forms of chronic pain. Morphine (10 mg/kg) was injected to rats intraperitoneally for 5 day. The variable dose of nalbuphine (0.1, 1.0 and 5.0 mg/kg) was administered (i.p.) in combination with morphine injection. The development of morphine tolerance was assessed by measuring the antinociceptive effect with the Randall-Selitto apparatus. The development of dependence on morphine was determined by the scoring the precipitated withdrawal signs for 30 min after injection of naloxone (10 mg/kg, i.p.). Nalbuphine did not attenuate antinociceptive effect of morphine in rats. Interestingly, combined administration of morphine with nalbuphine (10:1) significantly attenuated the development of dependence on morphine. The elevation of $[^3H]MK-801$ binding in frontal cortex, dentate gyrus, and cerebellum after chronic morphine infusion was suppressed by the coadministration of nalbuphine. In addition, the elevation of NR1 expression by morphine was decreased by the coadministration of nalbuphine in rat cortex. These results suggest that the coadministration of nalbuphine with morphine in chronic pain treatment can be one of therapies to reduce the development of tolerance to and dependence on morphine.