Zinc–Phosphorus Complex Working as an Atomic Valve for Colloidal Growth of Monodisperse Indium Phosphide Quantum Dots

Koh, Sungjun,Eom, Taedaehyeong,Kim, Whi Dong,Lee, Kangha,Lee, Dongkyu,Lee, Young Kuk,Kim, Hyungjun,Bae, Wan Ki,Lee, Doh C. American Chemical Society 2017 Chemistry of materials Vol.29 No.15

<P>Growth of monodisperse indium phosphide (InP) quantum dots (QDs) represents a pressing demand in display applications, as size uniformity is related to color purity in display products. Here, we report the colloidal synthesis of InP QDs in the presence of Zn precursors in which size uniformity is markedly enhanced as compared to the case of InP QDs synthesized without Zn precursors. Nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and mass spectrometry analyses on aliquots taken during the synthesis allow us to monitor the appearance of metal phosphorus complex intermediates in the growth of InP QDs. In the presence of zinc carboxylate, intermediate species containing Zn-P bonding appears. The Zn-P intermediate complex with P(SiMe3)(3) exhibits lower reactivity than that of the In P complex, which is corroborated by our prediction based on density functional theory and electrostatic potential charge analysis. The formation of a stable Zn P intermediate complex results in lower reactivity, which enables slow growth of QDs and lowers the extreme reactivity of P(SiMe3)(3), hence monodisperse QDs. Insights from experimental and theoretical studies advance mechanistic understanding and control of nucleation and growth of InP QDs, which are key to the preparation of monodisperse InP-based QDs in meeting the demand of the display market.</P>

Reconfigurable spintronic physical unclonable functions based on spin-orbit torques in ferromagnet/nonmagnet/ferromagnet trilayer structures

Soogil Lee,Jaimin Kang,Jeong-Mok Kim,Taek-Hyeon Lee,Sungjun Lee,Donghyeon Han,Sanghwa Lee,Kab-Jin Kim,Byong-Guk Park 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

Entering the era of Inter of Things (IOT), diverse smart devices generate and transfer enormous digital information. In this IOT environment, information security is becoming a critical issue because conventional software-based security technology is vulnerable to adversarial machine learning attacks. Thus, hardware-based security technology has been proposed to overcome this vulnerability, receiving much attention as an alternative. Especially, randomness of nature serves as an essential ingredient for the hardware-based security technology. For example, manufacturing processes of complementary-metal-oxide-semiconductor (CMOS) involves inevitable tolerances. Therefore, every electronic device is physically not identical despite the identical manufacturing processes. Those distinguishable device characteristics under the identical manufacturing process, so called “physical unclonable function (PUF)”, can potentially create non-identical output (response) under the identical input (challenge) generating unique identification of each electronic devices [1]. In this presentation, we demonstrate the spintronic PUF utilizing bottom-ferromagnet (FM)/nonmagnet/top-FM trilayer structures. Here, bottom and top FMs exhibit in-plane and perpendicular magnetic anisotropy, respectively. In these trilayer structures, field-free magnetization switching of top-FM is achieved by out-of-plane polarized spin current injection due to the interfacial spin precession mechanism, and the switching polarity is controlled by the in-plane magnetization direction of bottom-FM [2]. Under the identical demagnetization process of the bottom-FM, distinct magnetic domain distributions are formed on each identical wafer, consisting of a number of Hall-bar devices with random magnetization direction of bottom-FM along the demagnetization axis. These randomly distributed domains of bottom-FM on each wafer are electrically detected through the current-induced field-free spin-orbit torque switching polarity relies on the direction of bottom-FM. Therefore, these spintronic PUF wafers with unique pattern of domain distributions manifests itself as the unique electrical identification which can also be integrated into magnetic random access memory. Furthermore, we also discuss the reconfigurability and reliability of this spintronic PUF, providing great potential to hardware-based security applications because it is compatible with current CMOS technology.

드론 기반 병충해 예찰을 위한 통합 관제 시스템 설계

이대현 ( Daehyun Lee ),한길수 ( Kilsu Han ),이현동 ( Hyundong Lee ),김국환 ( Gookhwan Kim ),이명훈 ( Meonghun Lee ),김점순 ( Jeomsoon Kim ),홍성준 ( Sungjun Hong ),이경재 ( Kyongjae Lee ),송장훈 ( Janghoon Song ) 한국농업기계학회 2017 한국농업기계학회 학술발표논문집 Vol.22 No.2

최근 국내농업은 지구 온난화에 따른 기후변화와 국가 간 교역 확대, 해외여행 증가 등으로 인해 농산물 수입이 지속적으로 확장되고 있으며, 이는 검역병해충 및 외래·돌발 병해충의 발생 확산을 야기하여 농가의 병충해 피해를 증가시키고 있다. 특히, 이 중 과수 화상병의 경우 빠른 전염속도로 인해 발생 시과수원을 폐원시키므로 농가의 심각한 피해를 가져다주고 있어 문제해결이 시급한 실정이다. 국내에서는 병충해 관리를 위해 정기적인 예찰 및 방제를 수행하고 있지만 인력 활용 및 육안으로 감염 여부를 판정하고 있어 정확한 예찰이 어려울 뿐만 아니라 인력에 의한 병의 전파가 지속적으로 우려되고 있다. 드론은 무인비행장치로 최근 비행 제어 기술의 고도화로 인해 다양한 산업에서 그 활용범위가 급속도로 향상되고 있다. 농업분야의 경우 영상 장치의 소형화, 경량화를 통해 다양한 영상센서를 드론에 장착함으로써 농지의 다양한 정보의 실시간 측정이 가능하다. 따라서 본 연구에서는 드론 기반 항공 예찰을 위한 기초 연구로 항공예찰 영상의 분석 및 드론 이착륙 관리를 위한 통합 관제 시스템을 설계하였다. 통합 관제 시스템은 드론 이착륙을 위한 스테이션과 항공영상 수신 및 제어 신호 송신, 항공영상 DB 관리 및 영상 분석이 가능한 데이터 처리부로 구성된다. 이착륙 스테이션은 드론 보관을 위한 케이스 내부에 드론이착륙 지원을 위한 상하 리프트 제어와 착륙 플레이트, 기구부 등이 설치되며, 드론의 이착륙에 따라 루프가 자동 개폐되도록 설계되었다. 데이터 관리부는 수신된 항공 영상을 위치-예찰정보로 데이터베이스화한 후 이를 이용하여 영상학습 모델 기반 과수병 예찰영상 분석을 수행한다. 학습 영상 데이터는 각각의 항공 영상을 분할하여 훈련, 검증, 테스트 데이터로 분류하며, 훈련 데이터는 샘플 수 증가 및 오버피팅(over-fitting) 감소를 위해 잘라내기, 회전, 밝기/색상 변환 등 데이터 증강 후 사용된다. 영상학습 기반예찰 기술의 적용성은 사과 과수 화상병 항공영상을 이용하여 적용 가능성을 평가하였다. 본 시스템을 활용한 예찰 수행 시 인력 예찰 문제 해결 및 과수원의 항공영상 정보 수집의 자동화가 가능할 것으로 예측되며, 이를 위해서는 과수병 증상이 발현된 항공영상 관련 데이터베이스 구축을 통한 예찰 모델 정확도 향상과 최적화된 드론의 운행 제어를 통한 항공 예찰의 효율 향상이 필요할 것으로 판단된다.

Highly luminescent silica-coated CdS/CdSe/CdS nanoparticles with strong chemical robustness and excellent thermal stability

Wang, Nianfang,Koh, Sungjun,Jeong, Byeong Guk,Lee, Dongkyu,Kim, Whi Dong,Park, Kyoungwon,Nam, Min Ki,Lee, Kangha,Kim, Yewon,Lee, Baek-Hee,Lee, Kangtaek,Bae, Wan Ki,Lee, Doh C IOP 2017 Nanotechnology Vol.28 No.18

<P>We present facile synthesis of bright CdS/CdSe/CdS@SiO<SUB>2</SUB> nanoparticles with 72% of quantum yields (QYs) retaining ca 80% of the original QYs. The main innovative point is the utilization of the highly luminescent CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) as silica coating seeds. The significance of inorganic semiconductor shell passivation and structure design of quantum dots (QDs) for obtaining bright QD@SiO<SUB>2</SUB> is demonstrated by applying silica encapsulation via reverse microemulsion method to three kinds of QDs with different structure: CdSe core and 2 nm CdS shell (CdSe/CdS-thin); CdSe core and 6 nm CdS shell (CdSe/CdS-thick); and CdS core, CdSe intermediate shell and 5 nm CdS outer shell (CdS/CdSe/CdS-SQW). Silica encapsulation inevitably results in lower photoluminescence quantum yield (PL QY) than pristine QDs due to formation of surface defects. However, the retaining ratio of pristine QY is different in the three silica coated samples; for example, CdSe/CdS-thin/SiO<SUB>2</SUB> shows the lowest retaining ratio (36%) while the retaining ratio of pristine PL QY in CdSe/CdS-thick/SiO<SUB>2</SUB> and SQW/SiO<SUB>2</SUB> is over 80% and SQW/SiO<SUB>2</SUB> shows the highest resulting PL QY. Thick outermost CdS shell isolates the excitons from the defects at surface, making PL QY relatively insensitive to silica encapsulation. The bright SiO<SUB>2</SUB>-coated SQW sample shows robustness against harsh conditions, such as acid etching and thermal annealing. The high luminescence and long-term stability highlights the potential of using the SQW/SiO<SUB>2</SUB> nanoparticles in bio-labeling or display applications.</P>

Gait Recognition Using Decision-Level Fusion

Sungjun Hong,Heesung Lee,Byungyun Lee,Euntai Kim 대한전자공학회 2010 ICEIC:International Conference on Electronics, Inf Vol.1 No.1

For human identification, in this paper, a gait recognition system adopting decision-level fusion is proposed. The gait sequence obtained from a video camera is partitioned into multiple gait cycles selecting key frames summarizing a single stride. After gait cycle partitioning, the projection of a silhouette image called as a frieze pattern is calculated as a gait feature. To identify individual, the outputs of the nearest neighbor classifiers are fused by majority voting. To demonstrate the validity of the proposed method, the CASIA gait dataset A are used to evaluate the recognition performance.

A Low-Jitter Area-Efficient LC-VCO Based Clock Generator in 0.13-µm CMOS

LEE, Joonhee,KIM, Sungjun,JEON, Sehyung,LEE, Woojae,CHO, SeongHwan The Institute of Electronics, Information and Comm 2009 IEICE transactions on electronics Vol.92 No.4

<P>This letter presents an ultra low-jitter clock generator that employs an area-efficient LC-VCO. In order to fully utilize the area of the on-chip inductor, the loop filter of a phase locked loop (PLL) is located underneath the inductor. A prototype chip implemented in 0.13µm CMOS process achieves 105MHz to 225MHz of clock frequency while consuming 4.2mW from 1.2V supply. The measured rms jitter and normalized rms jitter of the proposed clock generator are 2.8ps and 0.031% at 105MHz, respectively.</P>

Gelatinous Transformation of Bone Marrow Mimicking Malignant Marrow-Replacing Lesion on Magnetic Resonance Imaging in a Patient without Underlying Devastating Disease

Lee, Joohee,Yoo, Yeon Hwa,Lee, Sarah,Kim, Hak Sun,Kim, Sungjun Korean Society of Magnetic Resonance in Medicine 2018 Investigative Magnetic Resonance Imaging Vol.22 No.1

Gelatinous transformation of bone marrow is characterized by hypoplasia of fat cells with focal loss of hematopoietic cells and deposition of extracellular gelatinous substances. It is known to be associated with devastating underlying diseases that starve bone marrow. Here, we present a case of a patient whose magnetic resonance (MR) imaging findings of vertebral column were interpreted as metastasis or hematologic malignancy, however, the final diagnosis revealed a gelatinous transformation of bone marrow. This is the first report of gelatinous transformation of bone marrow without evidence of underlying devastating disease.

The final report for CCM.M-K7: key comparison of 5 kg, 100 g, 10 g, 5 g and 500 mg stainless steel mass standards

Lee, Sungjun,Borys, Michael,Abbott, Patrick,Becerra, Luis Omar,Eltawil, Alaaeldin A,Jian, Wang,Malengo, Andrea,Medina, Nieves,Snegov, Victor,Wü,thrich, Christian,Scholz, Frank IOP 2017 Metrologia Vol.54 No.-

<P></P> <P>In order to show equivalence in mass standards calibration among National Metrology Institutes (NMIs) of member countries of the 'Comité international des poids et mesures' (CIPM), key comparisons (KC) of mass standards have been carried out under the auspices of the '<I>Comité Consultatif pour la Masse et les Grandeurs Apparentées</I>' (CCM). This key comparison of 5 kg, 100 g, 10 g, 5 g and 500 mg stainless steel mass standards was based on the decision of the CCM during the 12<SUP>th</SUP> meeting held in 2010 at the Bureau International des Poids et Mesures (BIPM). KRISS (Republic of Korea) and PTB (Germany) acted as pilot laboratory and co-pilot laboratory, respectively. The results were evaluated with the Monte Carlo method using measurement values based on participants' reference standards calculated following the recent BIPM amendments in 2015. Regarding participant results, VNIIM (100 g and 5 g) were not consistent with the key comparison reference values within their expanded uncertainties with the coverage factor, <I>k</I> = 2.</P> <P></P> <H2>Main text</H2> <P> To reach the main text of this paper, click on <A HREF='http://www.bipm.org/utils/common/pdf/final_reports/M/M-K7/CCM.M-K7.pdf'>Final Report</A>. Note that this text is that which appears in Appendix B of the BIPM key comparison database <A HREF='http://kcdb.bipm.org/'>kcdb.bipm.org/</A>.</P> <P>The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</P>

Tailoring the oxygen vacancy of cobalt-iron based electrocatalysts for OER via the mechanochemistry

Sungjun Heo,Chiho Kim,Song Jin,Jae-Yeop Jeong,Shinwoo Myeong,Hoseok Lee,Eonju Park,Namin Kim,Jae-hun Lee,Jun young park,Jooyoung Lee,Sung Mook Choi 한국표면공학회 2023 한국표면공학회 학술발표회 초록집 Vol.2023 No.11-1

Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression

Lee, Seungbo,Lee, Young Han,Chung, Tae-Sub,Jeong, Eun-Kee,Kim, Sungjun,Yoo, Yeon Hwa,Kim, In Seong,Yoon, Choon-Sik,Suh, Jin-Suck,Park, Jung Hyun The Korean Society of Radiology 2015 KOREAN JOURNAL OF RADIOLOGY Vol.16 No.6

<P><B>Objective</B></P><P>To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings.</P><P><B>Materials and Methods</B></P><P>A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD∩FA (considered positive when both the MD and FA results were positive), LD∩FA (considered positive when both the LD and FA results were positive), and RD∩FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard.</P><P><B>Results</B></P><P>The MD, LD, and RD cut-off values were 1.079 × 10<SUP>-3</SUP>, 1.719 × 10<SUP>-3</SUP>, and 0.749 × 10<SUP>-3</SUP> mm<SUP>2</SUP>/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (<I>p</I> = 0.003), FA and LD∩FA (<I>p</I> < 0.001), FA and RD∩FA (<I>p</I> < 0.001), MD and LD∩FA (<I>p</I> = 0.024) and MD and RD∩FA (<I>p</I> = 0.024).</P><P><B>Conclusion</B></P><P>Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.</P>