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Few atom thick, twisted bilayer graphene (tBLG) possesses a rotation angle (θ) dependent van Hove singularity (vHs). Fine-tuning vHs serves a potential method to enhance charge transfer (CT) in surface enhanced Raman spectroscopy. This study shows that tBLG having a specific θ promotes as high as a 1.7 times enhancement of the Raman signals of copper phthalocyanine (CuPc) as compared to that caused by single layer graphene (SLG). The results of a combination of reflection imaging spectroscopy and widefield Raman provide spatial and spectral information about both tBLG with θ ranging from 10.9 to 13.7° and the corresponding vHs. Comparison of Raman spectra of CuPc in presence and absence of tBLG demonstrates that a significant enhancement of certain CuPc vibrational modes occurs when the underlying tBLG possesses a θ = 12.2°, showing as high as 6.8 and 1.7 times enhancements of certain vibrational mode as compared to those of CuPc on bare and SLG substrates, respectively. Theoretical calculations indicate that a match between the energies of vHs of tBLG with those of frontier orbitals of CuPc facilitates CT from the distant SLG to CuPc.

Carbonaceous impurities (CIs) affect the optoelectronic properties as well as the ability to use absorption spectroscopy to estimate the metallic content of a single-walled carbon nanotube (SWNT) dispersion. Therefore, a method for the accurate quantification and removal of CIs is required. We have devised methods to characterize and quantify CIs present in SWNT batches and to determine the effects of CIs on the optical and electrical properties of SWNT. Quantitative determination of CIs stems from the finding that chloroform selectively disperses CIs present in SWNT batches. CIs separated by dispersing the as-purchased SWNT batch in chloroform have the morphology of defective and agglomerated few-layered graphenes, whose sizes and locations depend on SWNT batches. Moreover, CIs exhibit a featureless UV-vis-mid-wavelength IR (MWIR) absorption curve and an extinction coefficient comparable to graphenes and show difference with carbon black, which is frequently used as the CI reference. The MWIR region that shows least absorptions caused by the transition of various SWNT types was utilized to assess the significant contribution made by CIs present in a surfactant-assisted SWNT dispersion, showing about 12-19 wt% of CIs in various SWNT dispersions. In addition, the extraction of CIs with chloroform results in a highly purified SWNT batch without any diameter distribution change originating from oxidative damage as compared to the commercially available purified SWNT batch. Finally, we found that increasing the weight of CIs present in a SWNT dispersion strongly lowers the thermal conductivity of a SWNT film when compared with the electrical conductivity. This study provides a way to understand the negative effects that CI has on the optoelectronic properties of SWNTs as well as the beneficial effects of excluding ubiquitous CIs in SWNTs batches.

Facile construction of graphene nanostructures are potentially important for fundamental studies and various applications owing to its transparency and mechanical strength. Here we found that focused laser irradiation of a graphene/entrapped water/hydrophobic substrate leads to vaporization of entrapped water and consequent formation of graphene nanostructures. Graphene mechanically exfoliated on a hydrophobicized Si substrate was served as a transformable and impermeable nanocontainer in which water anisotropically and slowly diffuses from the weak edges into the van der Waals (vdW)-coupled interstitial volume between graphene and the substrate. Time-lapsed Raman mappings show that water entrapment promotes progressive lowering of the frequencies of the G and 2D bands of graphene and exhibits slower diffusion owing to vdW decoupling of substrate-induced doping and biaxial strain of graphene with hydrophobic substrate. Moreover, vaporized entrapped water promotes nanostructures by graphene sliding and bulging actions. This methodology represents viable approach to produce nanostructures from two dimensional materials.

Although solvent governed stability, selection and optical behavior of single walled carbon nanotubes (SWNTs) brought about by using specialized surfactants have importance in relation to various optoelectronic and biological applications, their origins and solvatochromism have not been thoroughly explored owing to the lack of ideal surfactant dispersing SWNTs. We show that solvent driven SWNT selection and solvatochromism occurs in SWNTs wrapped by two flavin derivatives in solvents with dielectric constants (e) ranging from 2.3 to 80.4. Flavin-SWNT nanocomposite dispersions exhibit near-armchair and chirality-specific enrichment in lower e aromatic solvents, and those with broader chirality selectivity are formed in higher e solvents. Those trends are also observed by controlling flavin concentration. Consideration of optical spectra provides relative quantum yields of flavin-SWNT in each solvent, showing toluene and p-xylene dispersions as best owing to highly individualized SWNT. The selectivities and relative stabilities of the flavin-SWNT nanoconjugates are associated with the solubility parameter (δ), which controls the respective morphology of the side chains and the relative Gibbs energies of the nanoconjugates relative to those of the free flavin and SWNTs. Differences between δ of side chains vs. the media results in extended and collapsed side chain conformations in respective lower and higher e solvents, leading to diameters (dt) selection of SWNT owing to diameter modulation of the isoalloxazine assembly. In addition, with increasing e optical transitions of flavin/SWNT exhibit lower bathochromic shifts owing to a passivating role played by the isoalloxazine that does not take place with other surfactants. The results suggest new guidelines for the design of good SWNT dispersions that take into consideration self-association of the surfactant, conformations of side chains and the nature of the solvent.

Despite the many advances that have been made in using anionic surfactants to disperse and sort single-walled carbon nanotubes (SWNTs) for optoelectronic applications, one-pot methods for deposition of SWNTs in a diameter (dt) and position controlled manner from as-dispersed sample are essential. Here, we designed and prepared flavin-containing self-assembled monolayers (flavin-SAMs) that can be used to assemble dt-selective individualized SWNT networks directly from SWNT dispersions by using the widely-used anionic surfactant. For a given glass substrate, the dimethallylsilane-linked azide, along with surface immobilization was employed to have Click reaction with terminal acetylene tethered to flavin group known to have strong affinity with SWNT. As demonstrated by atomic force microscopy and other methods, along successful assembly of individualized networks, the SWNTs are either fully or partially wrapped in a dt selective manner by isoalloxazine moieties tethered to the surface, displaying Langmuir isotherm adsorption behaviors in a dipping method dependent manner. The assembled SWNT network secures photoluminescence and electrical conductivity albeit its intimacy to underlying substrate and near monolayer coverage of SWNT network, respectively, and, furthermore, preferentially takes place on flavin-SAM over hydrophobic surface.

The development of novel methods to detect mercury is of paramount importance owing to the impact of this metal on human health and the environment. We observed that flavin mononucleotide (FMN) and its helical assembly with a single-walled carbon nanotube (SWNT) selectively bind Hg2+ arising from HgCl2 and MeHgCl. Absorption spectroscopic studies show that FMN preferentially forms a 2:1 rather than a 1:1 complex with Hg2+ at high FMN concentrations. On the basis of the analogy to the thymine–Hg–thymine complex, it is proposed that the 2:1 complex between FMN and Hg2+ comprises a Hg-bridged pair of FMN groups, regardless of the presence of SWNT. Upon addition of as little as a few hundred nanomoles of Hg2+, both FMN and FMN–SWNT exhibit absorption and photoluminescence (PL) changes. Moreover, FMN–SWNT displays simultaneous multiple sigmoidal changes in PL of SWNT tubes having different chiral vectors. Assessment of binding affinities using the Hill equation suggests that 2:1 and 1:1 complexes form between ...

Understanding the heterojunction of a lateral heterostructured transition metal dichalcogenide (hTMD) is important in order to take advantage of the combined optoelectronic properties of individual TMDs for various applications but, however, is hampered by mingled effects from lattice mismatch and substrate interaction. Here, we systematically investigated the strain occurring at lateral hTMDs consisting of molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) prepared by chemical vapor deposition. Comparison of homologous TMDs and hTMDs from controlled growth order revealed systematic change in photoluminescence behavior depending on substrate interaction and relative lattice mismatch. Near the heterojunction, a TMD with a larger lattice constant (a) exhibits photoluminescence (PL) red-shift, whereas a TMD with smaller a shows an opposite trend owing to lattice-induced strain. These effects are augmented in a subtractive or additive manner by tensile strain from the substrate interaction. Moreove...

Although the multiwalled carbon nanotube (MWNT) is a promising material for use in the production of high electrical conductivity (σ) polymer nanocomposites, its tendency to aggregate and distribute randomly in a polymer matrix is a problematic issue. In the current study, we developed a highly conductive and monoclinically aligned MWNT-polyamide 6 (PA) nanocomposite containing interfacing flavin moieties. In this system, the flavin mononucleotide (FMN) initially serves as a noncovalent aqueous surfactant for individualizing MWNTs in the form of FMN-wrapped MWNTs (FMN-MWNT), and then partially decomposed FMN (dFMN) induces crystallization of the PA on the MWNTs. The results of experiments performed using material subjected to partial dissolution of PA matrix show that the nanocomposite PA-dFMN-MWNT, formed by melt extrusion of PA and dFMN-MWNT, contains a three-dimensional monoclinic MWNT network embedded in an equally monoclinic PA matrix. An increase in monoclinic network promoted by an increase in the content of MWNT increases σ of the nanocomposite up to 100 S/m, the highest value reported for a polymer-MWNT nanocomposite. X-ray diffraction along with transmission electron microscopy reveal that the presence of dFMN induces the formation of monoclinic PA on dFMN-MWNT. The high σ of the PA-dFMN-MWNT nanocomposite is also a consequence of a minimization of defect formation of MWNT by noncovalent functionalization. Hierarchical structural ordering, yet individualization of MWNTs, provides a viable strategy to improve the physical property of nanocomposites.

Korean Abstract: 2018년 3월 트럼프 대통령이 중국에 대한 추가관세 부과를 결정한 이후 미ㆍ중 통상분쟁은 시작되었으며 현재까지 지속되고 있다. 본 보고서는 미국의 301조 조사 보고서와 화웨이 사태로 대표되는 미국의 대중 무역 및 투자 제재 확대에 근거하여 미ㆍ중 간 갈등의 본질이 관세전쟁이 아닌 기술패권 경쟁이라는 시각에 기반을 두고 작성되었다. 첨단기술의 발전은 안보 및 패권의 개념을 변화시키고 있다. 첨단기술은 민군겸용(民軍兼用, dual-use)이 가능하며, 앞으로는 첨단기술 개발에 투자할수록 경제적ㆍ군사적 패권에 가까워질 것으로 전망된다. 4차 산업혁명을 대표하는 5G, AI, 빅데이터 관련 기술, 로봇, 항공우주, 양자컴퓨터를 포함한 슈퍼컴퓨터 모두 민군겸용이라는 특징을 갖고 있다. 이에 따라 첨단기술과 관련된 중국의 부상은 미국의 경계심을 높이고 있다. 제2장에서는 중국의 과학기술 육성 정책, 첨단산업 육성 전략, 과학기술 인재 육성 전략을 살펴보았다. 중국 과학기술의 부상은 하루아침에 달성된 것이 아니다. 중국은 정부 수립 초기부터 기초과학, 국방과학, 항공우주 등의 과학기술 개발에 힘을 쏟았으며, 개혁개방 이후에는 경제건설이 국가의 중심과제가 됨에 따라 ‘과학기술이 생산력’이라는 인식 아래 과학기술 발전 정책을 일관되게 추진해왔다. 특히 최근 시진핑 정부는 전 세계를 주도하는 ‘혁신강국(革新強國)’ 건설을 목표로 글로벌 과학기술 패러다임의 변화에 발 빠르게 대응해오고 있다. 이러한 점은 각종 통계에서도 나타난다. 제3장에서는 중국이 현재 실질GDP(PPP 기준)와 무역 규모 면에서 세계 1위 국가이며, 군비지출, R&D지출 및 국제특허 출원 측면에서 미국에 이은 세계2위 국가로 성장한 사실을 각종 통계를 통해 살펴보았다. 또한 미ㆍ중 간 기술 격차를 이해하기 위해 국제특허 데이터를 이용하여 중국의 혁신생산성이 2014년 이후 미국을 추월하였다는 사실을 구조적 추정 모형(structural estimation model)을 사용하여 처음으로 밝혔다. 이를 바탕으로 제4장에서는 중국의 과학기술 부상에 대한 미국의 경계심과 대중제재에 대해 구체적으로 살펴보았다. 미국은 중국이 WTO 가입 이후 자유경쟁에 기반한 무역과 투자의 원칙을 받아들이지 않고 오히려 정부 주도의 중상주의 정책을 활용하여 성장했다고 인식하고 있다. 미국은 불법적이고 불공정하게 중국의 손에 넘어간 자국의 기술이 자국의 국가안보와 이익을 침해하는 데 사용되고 있다는 인식 아래, 중국에 대한 무역규제와 투자규제를 강화하고 있다. 본 연구에서는 구체적으로 「수출통제개혁법(ECRA)」과 「2019 국방수권법」 889조, 그리고 「외국인투자위험심사현대화법(FIRRMA)」의 내용과 적용사례 및 의미를 살펴보았다. 이러한 미국의 제재에 중국은 팃포탯(tit-for-tat)전략이 아닌 ‘새로운 대장정’ 전략으로 대응하고 있다. 다시 말하면 중국은 장기적 목표를 설정하고 제도 정비, 산업 정책 조정, 자체기술 개발 강화로 대응하고 있는 것이다. 제5장에서는 향후 미ㆍ중 간 갈등의 양상을 전망함으로써 한국경제에 미치는 영향을 진단하고 장ㆍ단기적 시사점을 제시하였다. 미ㆍ중 간 갈등이 없는 국제환경이 외교적으로나 경제성장 측면에서 우리에게 최선이다. 안보와 경제발전을 위해 굳건한 한미동맹을 기반으로 중국과의 협력도 강화해야 하는 한국의 입장에서는 미ㆍ중 간 갈등이 고조될수록 정책 선택의 여지가 줄어들고 이익의 공간이 좁아지기 때문이다. 그러나 미ㆍ중 갈등 및 기술패권 경쟁은 중국의 불공정한 관행, 코로나19 확산으로 인한 미국 내 초당적 반중정서, 갈등의 제도화, 중국의 강경한 자세 등의 이유로 장기화될 전망이다. 이러한 상황 속에서 한국으로서는 단기적으로 미국의 대중제재가 주는 반사이익을 기대하기보다는 오히려 미국의 대중제재 확대가 우리 경제에 미칠 수 있는 부정적인 영향에 유의하는 것이 중요해 보인다. 최근 미국의 대중 무역규제는 나날이 강화되고 있으며 금융제재로까지 확대될 조짐을 보이고 있다. 아이러니하게도 미국이 중국을 압박할수록 중국은 첨단기술의 국산화에 박차를 가할 것으로 보인다. 중국이 첨단산업 거의 전 분야에 걸쳐 이미 우리보다 앞서 나갈 가능성이 커 보인다는 점에서 우리의 과학기술, 산업, 경제의 미래를 위한 장기적이고 실질적인 전략이 절실히 필요한 시점이다. 또한 미ㆍ중 간 갈등이 심화될수록 양국 모두로부터 양자택일의 압력이 높아질 가능성이 크다. 그러나 최근의 중일(中日)관계가 보여주듯 상대국이 필요로 하는 것을 갖고 있다면 국익 실현을 위한 자율적 공간 확보가 가능함을 알 수 있다. 그리고 여기서 말하는 ‘상대국이 필요로 하는 것’이란 바로 ‘기술력’을 말한다. 우리는 기술혁신 역량에서 글로벌 경쟁력을 유지해야만 타국으로부터 존중받을 수 있고 타국과의 협력 기회도 존재하는 시대를 맞이하였다는 점을 유념해야 한다. English Abstract: Since March 2018, when President Trump decided to impose additional tariffs on $50 billion worth of Chinese imports, the U.S.-China trade dispute has continued to this day. This study was conducted from the viewpoint that the nature of the U.S.-China conflict is not a tariff war but essentially a technological rivalry, represented by the U.S. Section 301 report and U.S. sanctions against Huawei. Recent developments in technologies are changing the concept of national security and that of hegemonic competition. The key feature of technologies in the 4th Industrial Revolution is dual-use. Emerging technologies such as 5G, AI, big data, robotics, aerospace, supercomputers and quantum computer-related technologies can be used for both civilian and military purposes. The more you invest in the development of advanced technologies, the closer you will be to economic and military hegemony. Therefore, it is no wonder that the U.S. harbors great concerns facing the rise of China in these advanced technologies. Chapter 2 examines China’s science and technology development policy, high-tech industry development strategy, and national talent development plan. The rise of Chinese science and technology was not achieved overnight. Since the nation’s founding in 1949, China has always been devoted to developing science and technology. Especially after China’s reform and opening, as economic construction became the central task of the country, science and technology have been perceived as “productive power.” The recent Xi Jinping government continues to place emphasis on science and technology, and aims to build China as a world-leading “Innovative Power.” This is also reflected in various statistics. Chapter 3 describes the data that support the rise of China. China is now the world’s largest economy in terms of real GDP (USD PPP) and trade volume, and has grown into the world’s second-largest country following the U.S. in terms of military expenditures, R&D expenditures, and international patent applications. In addition, this study constructs a structural estimation model in which each country produces international patents using R&D expenditures and R&D researchers. Empirical results have presented novel findings indicating that China’s innovative productivity has surpassed that of the U.S. since 2015. In light of these developments, Chapter 4 discusses at great detail the U.S. sanctions against China. The U.S. views China as not adhering to the principles of market-based trade and investment systems, rather utilizing a form of state-led mercantilism following its accession to the WTO. Based on the perception that China has used illegally and unfairly acquired U.S. technologies to undermine the national security and foreign policy interests of the U.S., the U.S. is strengthening trade and investment sanctions against China. This study, in specific, investigates the backgrounds,contents, and actual applications of the Export Control Reform Act (ECRA), Article 889 of the 2019 National Defense Authority Act, and the Financial Foreign Investment Risk Assessment Modernization Act(FIRRMA). In return, China is responding to the U.S. sanctions with a new “Long March” strategy rather than a tit-for-tat strategy. In other words, China has been setting long-term goals and responding to the U.S. sanctions by improving institutional arrangements, refining industrial policies, and developing its own technologies. Chapter 5 diagnoses the impact of the U.S.-China rivalry on the Korean economy by predicting the possible scenarios of the U.S.-China tensions. An international environment without conflict between the U.S. and China is the best for Korea in terms of both national security and economic growth. This is because South Korea has to strengthen cooperation with China based on a solid ROK-U.S. alliance for security and economic development. The more the conflict between the U.S. and China intensifies, the less policy choices and room for profits are left to Korea. However, the conflict between China and the U.S. is expected to be prolonged due to several reasons including China’s unfair practices, bipartisan anti-Chinese sentiment in the U.S., the institutionalization of tensions, and China’s strong response to the U.S. measures. In the short run, it seems important for Korea to pay attention to the negative impacts that might occur due to the expansion of U.S. sanctions against China, rather than expecting the benefits that might be brought by the U.S. sanctions to delay China’s technological progress. Recently, there are signs of the U.S. sanctions against China even further expanding the scope to financial sectors. Ironically, increasing pressure from the U.S. is expected to further strengthen China’s R&D capabilities in advanced technology and accelerate its competitiveness in emerging industries. With the onset of the 4th Industrial Revolution, China is rapidly closing the quality gap and technology gap in major industries where Korea has a comparative advantage. If Korea does not adequately respond to changes, it may be difficult to maintain a comparative advantage over China. Thus, now that U.S.-China tensions are intensifying, Korea is facing a pivotal moment in determining the future path of its economy. Moreover, the greater the conflict rises between the U.S. and China, the likelihood increases of pressure being applied on Korea to choose between one or the other. However, as the recent China-Japan relations imply, if you have what the other country needs, it is possible to secure strategic autonomy to realize national interests. Facing the 4th Industrial Revolution, “what every country needs” is “technological power.” We must keep in mind that a cooperative partnership with others and respect from other countries can only be guaranteed when Korea maintains global competitiveness in innovation capacity.

High-end applications of single-walled carbon nanotube (SWNT) require detailed understanding of their binding affinity (Kd) with surfactants. Here, we quantitatively determined the comprehensive Kd and aggregation number (γ) of nine nonionic and anionic surfactants according to SWNT chirality. Photoluminescence (PL)-based titration using flavin mononucleotide (FMN)-SWNT complexes showing the largest redshifted optical transition enabled quantitative comparison of the surfactants and displayed distinct first and second regimes which correspond to partial and full replacements of FMN, respectively. Especially, the second transition exhibited sigmoidal PL change whose middle point denoted by the inverse of Kd slightly differs from critical micelle concentration of surfactant alone, depending on its functional groups. Moreover, nonionic surfactants displayed larger Kd and lower γ values than the anionic did. Specifically, Kd values between Pluronic F108 and sodium dodecyl sulfonate differ by four orders of magnitude. Such differences were rationalized in terms of the occupied volume of the micelle based on the hydrodynamic volume and γ. During the replacement, Kd and γ were affected by the degree of surfactant rearrangement induced by aging process, leading to more stable complex. Scaling the interactions between surfactant and SWNT provides useful guidelines to design novel SWNT sorting method using more than two surfactants.

Multi-walled carbon nanotube (MWNT) has many commercial applications. However, its broad use is limited by the surface-bound oxygen lowering its thermal stability. Here, we developed a facile method to enhance the oxidative thermal resistance of MWNTs that involves molecular coating promoted surface passivation. In the approach, ball milling is employed to self assemble flavin mononucleotide (FMN) helically around MWNTs through non-covalent interactions with no increased defects in MWNT. Upon high temperature oxidation, the ribityl phosphate side chain of FMN in the nanoconstruct undergoes partial decomposition to generate a corresponding isoalloxazine derivative on the surface of the MWNTs. Transmission electron microscopy reveals that the oxidatively annealed material is comprised of a tight isoalloxazine coating stacked on the sidewalls of the MWNT. The results of thermal gravimetric analysis studies show that the coating further elevates long-term stability and the energy barrier for oxidation of the MWNT by 28 kJ/mol from 113 kJ/mol for the bare MWNT. The role of the isoalloxazine coating is proposed to be surface passivation from molecular oxygen. As a consequence of the passivation, the maximum oxidative temperature of the MWNT is raised to 938 K as compared to that of 843 K for bare MWNT.

Scalable and simple methods for selective extraction of pure, semiconducting (s) single-walled carbon nanotubes (SWNTs) is of profound importance for electronic and photovoltaic applications. We report a new, one-step procedure to obtain respective large-diameter s- and metallic (m)-SWNT enrichment purity in excess of 99% and 78%, respectively, via interaction between the aromatic dispersing agent and SWNTs. The approach utilizes N-dodecyl isoalloxazine (FC12) as a surfactant in conjunction with sonication and benchtop centrifugation methods. After centrifugation, the supernatant is enriched in s-SWNTs with less carbonaceous impurities, whereas precipitate is enhanced in m-SWNTs. In addition, the use of an increased centrifugal force enhances both the purity and population of larger diameter s-SWNTs. Photoinduced energy transfer from FC12 to SWNTs is facilitated by respective electronic level alignment. Owing to its peculiar photoreduction capability, FC12 can be employed to precipitate SWNTs upon UV irradiation and observe absorption of higher optical transitions of SWNTs. A thin-film transistor prepared from a dispersion of enriched s-SWNTs was fabricated to verify electrical performance of the sorted sample and was observed to display p-type conductance with an average on/off ratio over 10(6) and an average mobility over 10 cm(2)/V·s.

Korean Abstract: 본 연구는 리쇼어링의 배경을 살펴본 후 리쇼어링 지원정책에 대한 효과성을 점검하고 이로부터 정책적 시사점을 도출하기 위해 여러 각도에서 리쇼어링을 연구하였다. 리쇼어링의 학술적 정의를 바탕으로 활용 가능한 통계를 이용해 국내 리쇼어링의 가능성을 예측하고 모형을 통해 리쇼어링 정책의 효과성을 검토하였다. 또한 한국을 비롯하여 미국, 유럽, 대만의 리쇼어링 현황과 정책을 비교 및 분석하였다. 본 연구의 분석 결과는 리쇼어링 현상 및 배경에 대한 이해의 폭을 넓히고, 리쇼어링 정책의 효율적인 설계를 위한 토대로 활용될 것으로 기대된다. English Abstract: Following the global financial crisis, some advanced countries recognized that the manufacturing sectors play an important role in mitigating the negative effects of the economic crisis. Also, as there has been some indication of firms bringing back manufacturing activities back to their home countries in recent years, reshoring has received broad attention by policy makers in advanced coutnries such as U.S. and Europe. Firms once offshored are relocating production back to the home country as production costs have significantly increased in emerging countries, and as they encounter a variety of difficulties such as low quality of products and low flexibility in production processes. The Korean government announced reshoring policies which provide reshoring firms with tax or subsidy incentives in December 2013. However, the policies appeared to be ineffective because only a very limited number of firms chose to reverse their previous offshoring decisions, leading to the concern that only a small number of firms are realizing the benefit of the reshoring policies. Therefore, this study aims to analyze the background of reshoring and effectiveness of reshoring policies from various angles. First of all, this study examines the definition of reshoring used in the literature and compares this with the concept of reshoring used in the media or policies. In addition, we infer the possibility of reshoring based on Korean firm data and develop a model to study the effectiveness of the reshoring policies. Lastly, we study reshoring trends and policies for Korea, U.S., Europe, and Taiwan to provide policy implications.

Symmetry breaking of single-walled carbon nanotubes (SWNTs) has profound effects on their optoelectronic properties that are essential for fundamental study and applications. Here, we show that isomeric SWNTs that exhibit identical photoluminescence (PL) undergo symmetry breaking by flavin mononucleotide (FMN) and exhibit dual PLs and different binding affinities (Ka). Increasing the FMN concentration leads to systematic PL shifts of SWNTs according to structural modality and handedness due to symmetry breaking. Density gradient ultracentrifugation using a FMN–SWNT dispersion displays PL shifts and different densities according to SWNT handedness. Using the optical titration method to determine the PL-based Ka of SWNTs against an achiral surfactant as a titrant, left- and right-handed SWNTs display two-step PL inflection corresponding to respective Ka values with FMN, which leads to the determination of the enantiomeric excess (ee) of the SWNT ensemble that was confirmed by circular dichroism measurement....

Recently, a portable US imaging system using smart devices is highlighted for enhancing the portability of diagnosis. Especially, the system combination can enhance the user experience during whole US diagnostic procedures by employing the advanced wireless communication technology integrated in a smart device, e.g., WiFi, Bluetooth, etc. In this paper, an effective post-phase rotation-based dynamic receive beamforming (PRBF-POST) method is presented for wireless US imaging device integrating US probe system and commercial smart device. In conventional, the frame rate of conventional PRBF (PRBF-CON) method suffers from the large amount of calculations for the bifurcated processing paths of in-phase and quadrature signal components as the number of channel increase. Otherwise, the proposed PRBF-POST method can preserve the frame rate regardless of the number of channels by firstly aggregating the baseband IQ data along the channels whose phase quantization levels are identical ahead of phase rotation and summation procedures on a smart device. To evaluate the performance of the proposed PRBF-POST method, the pointspread functions of PRBF-CON and PRBF-POST methods were compared each other. Also, the frame rate of each PRBF method was measured 20-times to calculate the average frame rate and its standard deviation. As a result, the PRBFCON and PRBF-POST methods indicates identical beamforming performance in the Field-II simulation (correlation coefficient = 1). Also, the proposed PRBF-POST method indicates the consistent frame rate for varying number of channels (i.e., 44.25, 44.32, and 44.35 fps for 16, 64, and 128 channels, respectively), while the PRBF-CON method shows the decrease of frame rate as the number of channel increase (39.73, 13.19, and 3.8 fps). These results indicate that the proposed PRBF-POST method can be more advantageous for implementing the wireless US imaging system than the PRBF-CON method.

There is increasing interest in the point-of-care US system using smart devices, such as a tablet PC and a smartphone, due to their high accessibility and portability. To meet this growing interest, our group recently has developed a smartphone-based portable US system but it only provided B-mode imaging. In this paper, we present the realization of the Color Doppler (C-mode) imaging on the aforementioned system to provide the functional information such as velocity of blood flow. The smartphone-based portable US system consists of a smart probe and a smartphone. To implement the C-mode processing, we redesign the sequence of the data acquisition on a FPGA (Spartan 6 LX150, Xilinx Inc., USA) of the smart US probe. On the other hand, in the smartphone (Galaxy S5 LTE-A SM-G906, Samsung Electronics Inc., Korea), a real-time C-mode back-end processing is implemented. The performance of the proposed C-mode imaging is evaluated by the phantom study and in vivo study. As a result, the developed system can provide the quantitative information of the velocity and the distribution of the blood flow by B&C-mode images. Also, as the view depth is 4 cm, the proposed C-mode image processing satisfies the requirement of the real-time operation by providing processing time of 22 msec shorter than the data acquisition time (i.e., 34 msec).

In a 3-D medical ultrasound imaging system, a matrix array probe with 2-D positioning of the elements allows high resolution of ultrasound images due to its capability of two-dimensional dynamic focusing. However, the hundreds (up to thousands) of elements in the matrix array make the fabrication of the transducers and cables challenging. In this paper1, to achieve high quality of 3-D ultrasound images with low hardware complexity, we introduce a column-based micro-beamformer (CMB) in which a column in the matrix array is considered as a sub-array and then elevational and lateral beamformings are sequentially conducted in the analog and digital stages, respectively. For the performance evaluation of the proposed beamformer, the beam pattern simulations are conducted and point-spread-functions are obtained. In addition, root-mean-square-errors (RMSEs) in round-trip time delays were measured over the depths. Compared to a conventional micro-beamformer, the CMB produced more tightly focused beam patterns and showed almost equivalent performance to that of fully sampled array. In the near field, the mean RMSEs of the proposed and conventional beamformers were 274 ns and 18.1 ns (improved 93.4% of delay accuracy), respectively.

In this paper, we present a smart US imaging system (SMUS) based on an android-OS smartphone, which can provide maximally optimized efficacy in terms of weight and size in point-of-care diagnostic applications. The proposed SMUS consists of the smartphone (Galaxy S5 LTE-A, Samsung., Korea) and a 16-channel probe system. The probe system contains analog and digital front-ends, which conducts beamforming and mid-processing procedures. Otherwise, the smartphone performs the back-end processing including envelope detection, log compression, 2D image filtering, digital scan conversion, and image display with custom-made graphical user interface (GUI). Note that the probe system and smartphone are interconnected by the USB 3.0 protocol. As a result, the developed SMUS can provide real-time B-mode image with the sufficient frame rate (i.e., 58 fps), battery run-time for point-of-care diagnosis (i.e., 54 min), and 35.0°C of transducer surface temperature during B-mode imaging, which satisfies the temperature standards for the safety and effectiveness of medical electrical equipment, IEC 60601-1 (i.e., 43°C).

A commonly used phase rotation beamforming (PRBF) technique in medical ultrasound scanners requires four multipliers to realise phase rotation (PR) in addition to two lowpass filters for quadrature demodulation for each channel. A new scheme is presented to reduce the computational complexity of PRBF without sacrificing image quality that uses only 16 PRs located behind inter-channel adders, regardless of the number of channels, each of which is dedicated for one of 16 quantised PR values using a step size of 2π/16.

Global warming will have far-reaching effects on our ecosystem. However, its effects on Antarctic soils have been poorly explored. To assess the effects of warming on microbial abundance and community composition, we sampled Antarctic soils from the King George Island in the Antarctic Peninsula and incubated these soils at elevated temperatures of 5°C and 8°C for 14 days. The reduction in total organic carbon and increase in soil respiration were attributed to the increased proliferation of Bacteria, Fungi, and Archaea. Interestingly, bacterial ammonia monooxygenase (amoA) genes were predominant over archaeal amoA, unlike in many other environments reported previously. Phylogenetic analyses of bacterial and archaeal amoA communities via clone libraries revealed that the diversity of amoA genes in Antarctic ammonia-oxidizing prokaryotic communities were temperature-insensitive. Interestingly, our data also showed that the amoA of Antarctic ammonia-oxidizing bacteria (AOB) communities differed from previously described amoA sequences of cultured isolates and clone library sequences, suggesting the presence of novel Antarctic-specific AOB communities. Denitrification-related genes were significantly reduced under warming conditions, whereas the abundance of amoA and nifH increased. Barcoded pyrosequencing of the bacterial 16S rRNA gene revealed that Proteobacteria, Acidobacteria, and Actinobacteria were the major phyla in Antarctic soils and the effect of short-term warming on the bacterial community was not apparent.