• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.25 no.3
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• pp.340-346
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• 2023

Bilateral distal anterior cerebral artery (DACA) aneurysms also called "kissing aneurysms" or "mirror aneurysm" are extremely rare, accounting for only 0.2% of all intracranial aneurysms. There have only been a few examples of mirror DACA aneurysms reported in the literature. Here, we report a rare case of mirror DACA aneurysm in a middle aged female with its successful clipping. Patient was admitted with severe headache and altered sensorium. Computed tomography (CT) head was suggestive of anterior inter-hemispheric hematoma. Digital subtraction angiography (DSA) was done which was suggestive of two distal anterior cerebral artery aneurysms located at same anatomical position. It was treated through microsurgical clipping. Mirror image DACA aneurysms are rare occurrence. All patients with ruptured DACA aneurysms should have angiography with 3D reconstruction studies. This aids in determining the aneurysm's morphology and planning treatment accordingly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2169-2177
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• 2015

This paper proposes a new pattern matching module to overcome the increased runtime of previous algorithm using RAM, which was designed to overcome cost limitation of hash-based algorithm using CAM (Content Addressable Memory). By adopting Merge FSM algorithm to reduce the number of state, the proposed module contains state block and entry block to use in RAM. In the proposed module, one input string is compared with multiple entry strings simultaneously using entry block. The effectiveness of the proposed pattern matching unit is verified by executing Snort 2.9 rule set. Experimental results show that the number of memory reads has decreased by 15.8%, throughput has increased by 47.1%, while memory usage has increased by 2.6%, when compared to previous methods.

• Journal of Chest Surgery
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• v.53 no.6
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• pp.392-399
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• 2020

Background: Surgical treatment of empyema thoracis in patients with chronic kidney disease is challenging, and few studies in the literature have evaluated this issue. In this study, we aim to report the surgical outcomes of empyema and to analyze factors predicting perioperative mortality in patients with chronic kidney disease. Methods: This retrospective study included data from 34 patients with chronic kidney disease (estimated glomerular filtration rate <60 mL/min/1.73 ㎡ for 3 or more months) who underwent surgery for empyema between 2012 and 2020. An analysis of demographic characteristics and perioperative variables, including complications, was carried out. Postoperative mortality was the primary outcome measure. Results: Patients' age ranged from 20 to 74 years with a 29-to-5 male-female ratio. The majority (n=19, 55.9%) of patients were in end-stage renal disease (ESRD) requiring maintenance hemodialysis. The mean operative time was 304 minutes and the mean intraoperative blood loss was 562 mL. Postoperative morbidity was observed in 70.5% of patients (n=24). In the subgroup analysis, higher values for operative time, blood loss, intensive care unit stay, and complications were found in ESRD patients. The mortality rate was 38.2% (n=13). In the univariate and multivariate analyses, poor performance status (Eastern Cooperative Oncology Group >2) (p=0.03), ESRD (p=0.02), and late referral (>8 weeks) (p<0.001) significantly affected mortality. Conclusion: ESRD, late referral, and poor functional status were poor prognostic factors predicting postoperative mortality. The decision of surgery should be cautiously assessed given the very high risk of perioperative morbidity and mortality in these patients.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2046-2050
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• 2008

현재까지 우리나라에서 주로 사용되고 있는 2차원 흐름 해석 모형은 미연방 도로국(U.S. Federal Highway Administration)과 연계하여 Brigham Young University에서 개발된 SMS(Surface-Water Modeling System)모형이다. SMS모형 중 이송 확산 모형으로는 RMA-4가 포함되나 이 모형은 최신 수치기법을 반영하지 못하는 등의 문제점들로 인해 실제 물리적 현상을 모의에 있어서 한계를 가지고 있다. 따라서 물리적 현상에 대한 적절한 모의를 위해 여러 개선과정을 거쳐 RAM4가 개발되었다. 본 연구를 위해 점적분 유사량 측정기(P-61)와 대하천 유속계를 사용하여 대상구간의 SS자료 및 유속의 2차원적 분포를 취득하였고, SMS의 Pre-processing 기능을 이용하여 유한요소망을 구성하였다. 구성된 유한요소망과 흐름모형인 RMA-2를 사용하여 대상구간의 유속장을 모의하였다. 이때 모의된 유속장과 현장에서 취득한 유속분포를 비교하여 RMA-2를 검증하였고, SS자료와 RAM4로 모의된 농도장을 비교하여 RAM4를 검증하였다. 검증된 두 모형을 바탕으로 대상 구간에서 다량의 점오염원이 투입되는 가상의 시나리오를 선정 및 적용하여 오염물 이송 및 확산 거동에 대해 살펴보았다. 본 연구의 대상 하천은 형산강으로써, 유역 내에 경주시와 포항시가 위치하고 이 두 도시를 잇는 산업도로가 형산강 본류 위를 지나고, 또한 두 도시를 관류하고 있어 다른 국가하천과 마찬가지로 지속적이고 안정적인 수질관리가 필요한 하천이다, 모의구간은 형산강 본류 중 No. 68(안강 수위관측소 상류 약 350 m)에서 No. 48(부조 수위관측소 하류 약 200 m)까지로서, 약 4.3 km 구간을 모의 하였다. 모의구간 시점에서 약 0.35 km 지점에 산업도로의 일부분인 강동대교, 0.98 km 지점에 왕신천 유입, 1.35 km 지점에 수중보, 1.8 km 지점에 국당1교, 3.2 km 지점에 국당2교가 위치하며 구간 내에는 만곡 및 사행, 특히 수중보 전 후로 사주가 발달해있어 2차원 흐름 및 이송확산 모의에 적합하다고 판단되었다.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.688-695
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• 2004

The capacitor contact barrier(CCB) layers have been introduced in the FeRAM integration to prevent the Pt/Al reaction during the back-end processes. Therefore, the interdiffusion and intermetallic formation in $Pt(1500{\AA})/Al(3000{\AA})$ film stacks were investigated over the annealing temperature range of $100\sim500^{\circ}C$. The interdiffusion in Pt/Al interface started at $300^{\circ}C$ and the stack was completlely intermixed after annealing over $400^{\circ}C$ in nitrogen ambient for 1 hour. Both XRD and SBM analyses revealed that the Pt/Al interdiffusion formed a single phase of $RtAl_2$ intermetallic compound. On the other hand, in the presence of TiN($1000{\AA}$) barrier layer at the Pt/Al interface, the intermetallic formation was completely suppressed even after the annealing at $500^{\circ}C$. These were in good agreement with the predicted effect of the TiN diffusion barrier layer. But the conventional TiN CCB layer could not perfectly block the Pt/Al reaction during the back-end processes of the FeRAM integration with the maximum annealing temperature of $420^{\circ}C$. The difference in the TiN barrier properties could be explained by the voids generated on the Pt electrode surface during the integration. The voids were acted as the starting point of the Pt/Al reaction in real FeRAM structure.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.21-30
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• 2000

Numerical design optimization techniques are implemented for the improvement of the ram accelerator performance. The design object is to find the minimum ram tube length required to accelerate projectile from initial velocity $V_o$ to target velocity $V_e$. The premixture is composed of $H_2$, $O_2$, $N_2$ and the mole numbers of these species are selected as design variables. The objective function and the constraints are linearized during the optimization process and gradient-based Simplex method and SLP(Sequential Linear Programming) have been employed. With the assumption of two dimensional inviscid flow for internal flow field, the analyses of the nonequilibrium chemical reactions for 8 steps 7 species have been performed. To determined the tube length, ram tube internal flow field is assumed to be in a quasi-steady state and the flow velocity is divided into several subregions with equal interval. Hence the thrust coefficients and accelerations for corresponding subregions are obtained and integrated for the whole velocity region. With the proposed design optimization techniques, the total ram tube length had been reduced 19% within 7 design iterations. This optimization procedure can be directly applied to the multi-stage, multi-premixture ram accelerator design optimization problems.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.307-307
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• 2014

정보화 시대로 접어들면서 동일한 공간에 더 많은 정보를 저장할 수 있고, 보다 빠른 동작이 가능한 비휘발성 메모리 소자에 대한 요구가 증가하고 있다. 하지만, 최근 비휘발성 메모리 소자 관련 연구보고에 따르면, 메모리 소자의 소형화 및 직접화 측면에서, 전하 저장을 기반으로 하는 기존의 Floating-Gate(FG) Flash 메모리는 20 nm 이하 공정에서 한계가 예측 되고 있다. 따라서, 이러한 FG Flash 메모리의 한계를 해결하기 위해, 기존에 FET 기반의 FG Flash 구조와 같은 3 terminal이 아닌, Diode와 같은 2 terminal로 동작이 가능한 ReRAM, PRAM, STT-MRAM, PoRAM 등 저항변화를 기반으로 하는 다양한 종류의 차세대 메모리 소자가 연구되고 있다. 그 중, 저항 변화 메모리(ReRAM)는 CMOS 공정 호환성, 3D 직접도, 낮은 소비전력과 빠른 동작 속도 등의 우수한 동작 특성을 가져 차세대 비휘발성 메모리로 주목을 받고 있다. 또한, 상하부 전극의 2 terminal 만으로 소자 구동이 가능하기 때문에 Passive Crossbar-Array(CBA)로 적용하여 플래시 메모리를 대체할 수 있는 유력한 차세대 메모리 소자이다. 하지만, 이를 현실화하기 위해서는 Passive CBA 구조에서 발생할 수 있는 Read Disturb 현상, 즉 Word-Line과 Bit-Line을 통해 선택된 소자를 제외하고 주변의 다른 소자를 통해 흐르는 Sneak Leakage Current(SLC)를 차단하여 소자의 메모리 State를 정확히 sensing하기 위한 연구가 선행 되어야 한다. 따라서, 현재 이러한 이슈를 해결하기 위해서, 많은 연구 그룹에서 Diodes, Threshold Switches와 같은 ReRAM에 Selector 소자를 추가하는 방법, 또는 Self-Rectifying 특성 및 CRS 특성을 보이는 ReRAM 구조를 제안 하여 SLC를 차단하고자 하는 연구가 시도 되고 있지만, 아직까지 기초연구 단계로서 아이디어에 대한 가능성 정도만 보고되고 있는 현실 이다. 이에 본 논문은 Passive CBA구조에서 발생하는 SLC를 해결하기 위한 새로운 아이디어로써, 본 연구 그룹에서 선행 연구로 확보된 안정적인 저항변화 물질인 SiN를 정류 특성을 가지는 n-Si/Ti 기반의 Schottky Diode와 결합함으로써 기존의 CBA 메모리의 Read 동작에서 발생하는 SLC를 차단 할 수 있는 1SD-1R 구조의 메모리 구조를 제작 하였으며, 본 연구 결과 기존에 문제가 되었던 SLC를 차단 할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.326-326
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• 2014

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states [1-3]. We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.722-725
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• 2013

In this work, we have been analyzed the characteristics of ReRAM with different annealing condition and temperature. The ReRAM devices with top electrode=150nm, bottom electrode=150nm, oxide thickness=70nm and annealing temperature=$500^{\circ}C$, $850^{\circ}C$ have been used in characterization. The Set/Reset voltage, sensing window and resistivity have been characterized. From the measurement results, the Set/Reset voltage and sensing window have been enhanced as the annealing temperature has been increased. But it has been decreased as the temperature performance has been increased. In case of the annealing temperature=$850^{\circ}C$, the variation of Set/Reset voltage was lower than that of other condition. But the variation of sensing window was the lowest when the annealing temperature was $500^{\circ}C$. With considering the variation of Set/Reset voltage and sensing window, the devices annealed at $850^{\circ}C$ showed the best performance to ReRAM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.948-953
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• 2010

In this paper, we propose multi-bit soft error detection method which can use an instruction cache of superscalar CPU architecture. Proposed method is applied to high-speed static RAM for instruction cache. Using 1D parity and interleaving, it has less memory overhead and detects more multi-bit errors comparing with other methods. It only detects occurrence of soft errors in static RAM. Error correction is treated like a cache miss situation. When soft errors are occurred, it is detected by 1D parity. Instruction cache just fetch the words from lower-level memory to correct errors. This method can detect multi-bit errors in maximum 4$\times$4 window.