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Observation of molecular orbital gating
Song, Hyunwook,Kim, Youngsang,Jang, Yun Hee,Jeong, Heejun,Reed, Mark A.,Lee, Takhee Macmillan Publishers Limited. All rights reserved 2009 Nature Vol.462 No.7276
The control of charge transport in an active electronic device depends intimately on the modulation of the internal charge density by an external node. For example, a field-effect transistor relies on the gated electrostatic modulation of the channel charge produced by changing the relative position of the conduction and valence bands with respect to the electrodes. In molecular-scale devices, a longstanding challenge has been to create a true three-terminal device that operates in this manner (that is, by modifying orbital energy). Here we report the observation of such a solid-state molecular device, in which transport current is directly modulated by an external gate voltage. Resonance-enhanced coupling to the nearest molecular orbital is revealed by electron tunnelling spectroscopy, demonstrating direct molecular orbital gating in an electronic device. Our findings demonstrate that true molecular transistors can be created, and so enhance the prospects for molecularly engineered electronic devices.
Combing non-epitaxially grown nanowires for large-area electronic devices
Song, Hyunwook,Lee, Min Hyung IOP Pub 2013 Nanotechnology Vol.24 No.28
<P>A facile route for aligning randomly oriented nanowires synthesized by a vapor–liquid–solid method for the fabrication of nanoelectronic devices was achieved using a polymer combing technique. By controlling the Young’s modulus of the polymer combs, van der Waals interactions and shearing forces between the combs and nanowires can be manipulated and thus the nanowire density and alignment can be controlled. Using the proposed method, field-effect transistors were directly fabricated on as-grown substrates after aligning the nanowires, thereby demonstrating the feasibility of the scheme for the production of nanoelectronic devices.</P>
Inelastic electron tunneling spectroscopy of molecular transport junctions
Song, Hyunwook,Lee, Takhee,Reed, Mark Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10
Inelastic electron tunneling spectroscopy (IETS) has become a premier analytical tool in the investigation of nanoscale and molecular junctions. The IETS spectrum provides invaluable information about the structure, bonding, and orientation of component molecules in the junctions. One of the major advantages of IETS is its sensitivity and resolution at the level of single molecules. This review discusses how IETS is used to study molecular transport junctions and presents an overview of recent experimental studies.
Single Molecule Electronic Devices
Song, Hyunwook,Reed, Mark A.,Lee, Takhee WILEY‐VCH Verlag 2011 Advanced Materials Vol.23 No.14
<P><B>Abstract</B></P><P>Single molecule electronic devices in which individual molecules are utilized as active electronic components constitute a promising approach for the ultimate miniaturization and integration of electronic devices in nanotechnology through the bottom‐up strategy. Thus, the ability to understand, control, and exploit charge transport at the level of single molecules has become a long‐standing desire of scientists and engineers from different disciplines for various potential device applications. Indeed, a study on charge transport through single molecules attached to metallic electrodes is a very challenging task, but rapid advances have been made in recent years. This review article focuses on experimental aspects of electronic devices made with single molecules, with a primary focus on the characterization and manipulation of charge transport in this regime.</P>
Single‐Molecule Devices: Single Molecule Electronic Devices (Adv. Mater. 14/2011)
Song, Hyunwook,Reed, Mark A.,Lee, Takhee WILEY‐VCH Verlag 2011 Advanced materials Vol.23 No.14
<P><B>Abstract</B></P><P>Single molecule electronic devices in which individual molecules are utilized as active electronic components constitute a promising approach for the ultimate miniaturization and integration of electronic devices in nanotechnology through the bottom‐up strategy. Thus, the ability to understand, control, and exploit charge transport at the level of single molecules has become a long‐standing desire of scientists and engineers from different disciplines for various potential device applications. Indeed, a study on charge transport through single molecules attached to metallic electrodes is a very challenging task, but rapid advances have been made in recent years. This review article focuses on experimental aspects of electronic devices made with single molecules, with a primary focus on the characterization and manipulation of charge transport in this regime.</P>
Song Hyunwook,Jeon Seungik,Shin Yerim,한우재,Kim Saea,Kwak Chanbeom,Lee Eunsung,Kim Jinsook 대한청각학회 2022 Journal of Audiology & Otology Vol.26 No.2
Background and Objectives: Natural and synthetic speech signals effectively stimulate cortical auditory evoked potential (CAEP). This study aimed to select the speech materials for CAEP and identify CAEP waveforms according to gender of speaker (GS) and gender of listener (GL).Subjects and Methods: Two experiments including a comparison of natural and synthetic stimuli and CAEP measurement were performed of 21 young announcers and 40 young adults. Plosive /g/ and /b/ and aspirated plosive /k/ and /p/ were combined to /a/. Six bisyllables–/ga/-/ka/, /ga/-/ba/, /ga/-/pa/, /ka/-/ba/, /ka/-/pa/, and /ba/-/pa/–were formulated as tentative forwarding and backwarding orders. In the natural and synthetic stimulation mode (SM) according to GS, /ka/ and /pa/ were selected through the first experiment used for CAEP measurement.Results: The correction rate differences were largest (74%) at /ka/-/ pa/ and /pa/-/ka/; thus, they were selected as stimulation materals for CAEP measurement. The SM showed shorter latency with P2 and N1-P2 with natural stimulation and N2 with synthetic stimulation. The P2 amplitude was larger with natural stimulation. The SD showed significantly larger amplitude for P2 and N1-P2 with /pa/. The GS showed shorter latency for P2, N2, and N1-P2 and larger amplitude for N2 with female speakers. The GL showed shorter latency for N2 and N1-P2 and larger amplitude for N2 with female listeners.Conclusions: Although several variables showed significance for N2, P2, and N1-P2, P1 and N1 did not show any significance for any variables. N2 and P2 of CAEP seemed affected by endogenous factors.
Kim, Hyunwook,Kim, Kyoung Hoon,Park, Kisoo,Kang, Shin-Wook,Yoo, Tae-Hyun,Ahn, Song Vogue,Ahn, Hyeong Sik,Hann, Hoo Jae,Lee, Shina,Ryu, Jung-Hwa,Kim, Seung-Jung,Kang, Duk-Hee,Choi, Kyu Bok,Ryu, Dong-Ry Springer-Verlag 2014 Kidney international Vol.86 No.5
To date, only a few large-scale studies have measured the effect of dialysis modality on mortality in Asian populations. Here, we sought to compare survival between incident hemodialysis (HD) and peritoneal dialysis (PD) patients using the Korean Health Insurance Review & Assessment Service database. This enabled us to perform a population-based complete survey that included 32,280 incident dialysis patients and followed them for a median of 26.5 months. To reduce biases due to nonrandomization, we first matched 7049 patient pairs with similar propensity scores. Using the log-rank test, we found the mortality rate in PD patients was significantly higher than that in HD patients. Subsequent subgroup analyses indicated that in older patients (55 years and older), with the exception of the subgroup of patients with no comorbidities and the subgroup of patients with malignancy, PD was consistently associated with a higher mortality rate. In younger patients (under 55 years), regardless of the covariates, the survival rate of PD patients was comparable to that of HD patients. Thus, while the overall mortality rate was higher in incident PD patients, mortality rates of some incident PD and HD patients were comparable in Korea.
김현욱 ( Hyunwook Kim ),서혜경 ( Hyekyung Seo ),명준표 ( Jun-pyo Myong ),윤종서 ( Jong-seo Yoon ),송윤근 ( Yeunkun Song ),김충범 ( Choongbuem Kim ) 한국산업보건학회 (구 한국산업위생학회) 2016 한국산업보건학회지 Vol.26 No.3
Objectives: No 3D anthropometric analyses have been conducted for Korean children’s faces for the purpose of designing respiratory protective devices. The aim of this study was to develop masks against yellow dust and fine particulates, particularly for children in Korea. Methods: This study utilized a 3D scanning method to obtain 16 facial anthropometric data from children, ages of 5 to 13 years old. A total of 144 boys and girls were recruited from the kindergarten, elementary schools and middle schools in Seoul. With facial dimensions obtained, cluster analysis was performed to categorize them into similar facial groups. For each cluster, an optimal mask was designed and manufactured using a 3D printer. In addition, lung function data were obtained from 62 subjects and compared with those of normal adults. The pulmonary physiological results were subsequently used to suggest a test method for mask certification. Results: Facial shapes were classified into tree clusters: small, medium, and large. The face width and length for the first group were small with high nosal protrusion. The face width and length for the second group were the largest among the three clusters. The third group had the largest angle of nose root - gnathion(n-prn-gn). Age was the most significant variable in the facial dimensions. Children’s pulmonary physiological capacity was about 60% of adults’ capacity. The results of fit test using the prototype masks developed showed very good fits for children. Conclusions: For Korean children, three mask sizes will be sufficient and practical for providing protection against yellow dust and fine particulates. Anthropometric data obtained using digitalized 3D face analysis can be very effective for designing respiratory devices. 3D images can be accurate and easily measured for multiple dimensions, particularly for curved areas of the face. It is imperative to adopt different test methods for certifying respiratory protective devices for children, since their pulmonary physiological capacity is inferior compared with that of adults.