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Lasing at topological edge states in a photonic crystal L3 nanocavity dimer array
Han, Changhyun,Lee, Myungjae,Callard, Sé,golè,ne,Seassal, Christian,Jeon, Heonsu Nature Publishing Group UK 2019 Light, science & applications Vol.8 No.1
<▼1><P>Topological photonics have provided new insights for the manipulation of light. Analogous to electrons in topological insulators, photons travelling through the surface of a topological photonic structure or the interface of two photonic structures with different topological phases are free from backscattering caused by structural imperfections or disorder. This exotic nature of the topological edge state (TES) is truly beneficial for nanophotonic devices that suffer from structural irregularities generated during device fabrication. Although various topological states and device concepts have been demonstrated in photonic systems, lasers based on a topological photonic crystal (PhC) cavity array with a wavelength-scale modal volume have not been explored. We investigated TESs in a PhC nanocavity array in the Su–Schrieffer–Heeger model. Upon optical excitation, the topological PhC cavity array realised using an InP-based multiple-quantum-well epilayer spontaneously exhibits lasing peaks at the topological edge and bulk states. TES characteristics, including the modal robustness caused by immunity to scattering, are confirmed from the emission spectra and near-field imaging and by theoretical simulations and calculations.</P></▼1><▼2><P><B>Shrinking topological state lasers</B></P><P>Tiny lasers that emit light from single nano-sized cavities are becoming possible thanks to exotic photonic features called topological edge states (TESs) on the edges of a cavity array. TESs can steer neatly around obstacles without scattering out; this makes them ideal for navigating the inevitable imperfections that appear when fabricating nanostructures. Heonsu Jeon and co-workers at Seoul National University, Republic of Korea, and Université de Lyon, France, etched patterns of holes a few hundred nanometres apart in photoluminescent wafers, then directed a 1064-nanometre laser to optically excite their sample. They observed an isolated peak of stimulated emission around 1500 nanometres from one cavity, attributed to a TES. This evidence of lasing from sources even smaller than the wavelength of light could enable further minimising of photonic devices and have applications for quantum computing.</P></▼2>
3㎚급 Multi-Nanosheet Field Effect Transistor의 Bottom Oxide 및 Package에 따른 Self-Heating 변화
유창현(Changhyun Yoo),김현우(Hyunwoo Kim),선윤근(Yoongeun Seon),강명곤(Myounggon Kang),전종욱(Jongwook Jeon) 대한전자공학회 2021 전자공학회논문지 Vol.58 No.4
반도체 디바이스의 미세화가 지속적으로 진행됨에 따라 FinFET 또는 gate-all-around(GAA)구조와 같은 3차원 구조로 발전하고 있다. 하지만 미세화가 진행될수록 소자의 단위면적당 발열량이 증가하고 있고, 3차원 구조는 기존의 planar MOSFET에 비해 채널에서 발생하는 열을 방출하기가 더 어렵다. 물질의 크기가 작아지면서 열전도율이 나빠져 self-heating effect(SHE)가 심화되고 있다. 따라서 3차원 반도체 소자 구조의 SHE에 대한 연구가 활발히 진행되고 있다. 이 논문에서는 3㎚ 이하의 기술에서 사용될 유력한 후보인 multi-nanosheet field effect transistor(NSFET)의 다양한 공정 옵션을 변경하여 연구를 수행하였다. 이전의 SHE 연구는 주로 디바이스의 FEOL 내부 공정 옵션에 대한 것이었다. 하지만 이 논문에서는 패키징 방식과 BEOL 유전체 재료 및 bottom oxide의 도입 유무에 따른 SHE를 연구하였다. NSFET을 시뮬레이션하기 위해 3D TCAD 소프트웨어를 사용하였으며, 패키지 방식에 따른 열적 경계조건을 고려하였다. 연구 결과 bottom oxide는 나노 시트 채널에서 발생하는 열이 substrate로 방출되는 것을 막아 채널의 SHE으로 인한 최대온도 상승 값(△Tmax)을 높인 것으로 확인되었다. 반면 패키징 타입을 face-down으로 할 경우와 BEOL 유전물질의 열전도율이 높을수록 Rth와 △Tmax의 정도가 작아지는 것으로 확인되었다. As semiconductor devices are continuously miniaturized, heat generation per unit area is increasing. In addition, recently used FinFET structures or Gate-All-Around(GAA) structures such as nanosheets make it more difficult to dissipate heat generated in the channel compared to conventional planar MOSFETs. Therefore, many studies have been conducted on self-heating phenomenon in 3D semiconductor device structure. In this study, research was conducted by changing various process options in lateral multi-nanosheet FET, which is expected tobe used in technology nodes below 3㎚. While most of the previous self-heating studies were on the internal process option of the device FEOL, in this study, the self-heating effect by the package type, BEOL dielectric material, and device bottom isolation dielectric was studied. For this study, 3D TCAD software was used, and the thermal boundary according to the package type published in the previous paper[7] was considered. As a result of the analysis, it was confirmed that the bottom oxide prevented theheat generated from the nanosheet channel from being lost to the bottom substrate, thereby increasing the maximum temperature increase(△Tmax) value due to self-heating in the channel. It has been confirmed that when the packaging type is face-down and the higher the thermal conductivity of the dielectric material, the lower the degree of Rth and △Tmax.
생성적 적대 신경망(GAN)을 이용한 시계열 데이터 증강 기법 적용 및 성능 평가에 관한 연구
이창현(ChangHyun Lee),신동훈(DongHun Shin),전호석(HoSeok Jeon),정진우(JinWoo Jung),권기원(KiWon Kwon),임태호(TaeHo Im) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
본 논문은 시계열 데이터의 수집이 원활하게 이루어지지 못하는 것을 증강기법을 통해 해결하고자 제안된 방법이다. 특히 시계열 데이터 증강은 적은 양의 데이터로 높은 정확성을 나오게 하는 것이 중요하다. 데이터 증강을 인공지능을 사용해서 진행하기 위해 생성적 적대 신경망(GAN)을 이용하여 시계열 데이터 증강을 진행하였고, Test 데이터 세트로 확인을 했을 때 평균적으로 높은 정확성을 보여주었기에 시계열 데이터가 부족한 상황에서 생성적 적대 신경망(GAN)을 통해 데이터 증강을 진행했을 때 충분히 사용 가능하다는 것을 증명하였다.
급성 뇌경색을 동반한 당뇨 환자에게 Dapagliflozin 투여 후 발생한 급성 신손상 1예
박창현 ( Changhyun Park ),이은경 ( Eun Kyoung Lee ),김소미 ( So Mi Kim ),조종태 ( Jong Tae Cho ),이도현 ( Do Hyun Lee ),이지은 ( Ji-eun Lee ),전지현 ( Ji Hyun Jeon ) 대한내과학회 2020 대한내과학회지 Vol.95 No.6
Dapagliflozin is a recently developed oral anti-diabetic drug and SGLT2 inhibitor with well-known cardioprotective and renoprotective effects. Although a reduction of the glomerular filtration rate is induced by volume depletion and tubule-glomerular feedback during the early period after administering a SGLT2 inhibitor, the renal prognosis improves more with a decrease of proteinuria. However, the risk of acute kidney injury increases in heart failure and hypovolemia patients, and in those taking certain drugs, such as non-steroidal anti-inflammatory drugs, angiotensin-converting enzyme inhibitor/angiotensin II receptor blockers, or diuretics. We report acute kidney injury after dapagliflozin administration in a diabetic patient with acute cerebral infarction accompanied by right hemiplegia, motor aphasia, and dysphagia. (Korean J Med 2020;95:404-408)
Highly Sensitive Stretchable Electronic Skin with Isotropic Wrinkled Conductive Network
( Seung Hwan Jeon ),( Hyeongho Min ),( Jihun Son ),( Tae Kon Ahn ),( Changhyun Pang ) 한국센서학회 2024 센서학회지 Vol.33 No.1
Soft-pressure sensors have numerous applications in soft robotics, biomedical devices, and wearable smart devices. Herein, we present a highly sensitive electronic skin device with an isotropic wrinkled pressure sensor. A conductive ink for soft pressure sensors is produced by a solution process using polydimethylsiloxane (PDMS), poly 3-hexylthiophene (P3HT), carbon black, and chloroform as the solvents. P3HT provides high reproducibility and conductivity by improving the ink dispersibility. The conductivity of the ink is optimized by adjusting the composition of the carbon black and PDMS. Soft lithography is used to fabricate a conductive elastic structure with an isotropic wrinkled structure. Two conductive elastic structures with an isotropic wrinkle structure is stacked to develop a pressure sensor, and it is confirmed that the isotropic wrinkle structure is more sensitive to pressure than when two elastic structures with an anisotropic wrinkle structure are overlapped. Specifically, the pressure sensor fabricated with an isotropic wrinkled structure can detect extremely low pressures (1.25 Pa). Additionally, the sensor has a high sensitivity of 15.547 kpa<sup>-1</sup> from 1.25 to 2500 Pa and a linear sensitivity of 5.15 kPa<sup>-1</sup> from 2500 Pa to 25 kPa.
Seong Won Jeon,Nuri Lee,Ki Hong Lee,Minjeong Ha,Changhyun Kim,Yoo Ri Kim,Nam Sik Yoon,Hyung Wook Park 대한내과학회 2024 The Korean Journal of Internal Medicine Vol.39 No.3
Background/Aims: The SAMe-TT2R2 score is used for assessing anticoagulation control (AC) quality with warfarin. However, it is hard to apply SAMe-TT2R2 score in Asian patients with atrial fibrillation (AF), because it has not been proven in those populations. This study aimed to validate the SAMe-TT2R2 score in Asian patients with AF and suggest a modified SAMe- TT2R2 score for this population. Methods: We analyzed 710 Korean patients with AF who were using warfarin. The AC quality was assessed as the mean time in therapeutic range (TTR). Each component of SAMe-TT2R2 score was evaluated for the relationship with AC. Further clinical factors that predict AC were analyzed. Identified factors were re-assorted and constructed as SA2Me-TTR scoring system. Results: Of the components of the SAMe-TT2R2 score, female, age, and rhythm control were associated with AC. Heart failure and renal insufficiency were newly identified factors associated with AC. The modified SA2Me-TTR score was reconstructed with the relevant risk factors (S, female gender, 1 point; A, age < 60 yr, 2 points; Me, medical history of heart failure, 1 point; T, treatment for rhythm control, 1 point; T, history of stroke or transient ischemic attack, 1 point; R, renal insufficiency, 1 point). The modified SA2Me-TTR score demonstrated an excellent relationship with the grading of AC. The modified SA2Me-TTR score ≤ 1 identified patients with good AC (hazard ratio 2.46, 95% CI 1.75–3.47). Conclusions: The modified SA2Me-TTR score was useful for guiding oral anticoagulants selection in Asian patients with AF.