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Applicability of cement-based grout for ground heat exchanger considering heating-cooling cycles

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Science China(Technological Sciences) 2011年第7期54卷 1661-1667页

作者： Moonseo PARK Sunhongmin Jeehee LIM jong min choi Hangseok choi School of civil Environmental and Architectural Engineering Korea University Seoul Republic of Korea Department of Mechanical Engineering Hanbat National University Daejeon Republic of Korea

The applicability of cement grout （or cement-based grout） has been considered as an alternative to bentonite grout commonly used to backfill closed-loop vertical ground heat exchangers. In a geothermal heat pump system, repeated heating-cooling cycles may cause adverse effects on the integrity of cement grout in the ground heat exchanger. To account for the temperature cycling effect, the strength degradation of cement grout due to temperature cycling has been examined by measuring the unconfined compression strength of cured specimens in a humidity-temperature controlling chamber with applying temperature cycles between -5℃ and 50℃. There is a tendency that the unconfined compression strength decreases with an increase in the number of temperature cycles. On the other hand, an equivalent hydraulic conductivity of a pipe-embedded cement grout specimen was evaluated by carrying out a modified flexible wall permeameter test equipped with a water circulating system to control temperature inside the pipe section. The applied operating temperature range was from 5 to 35℃. After three cycles of heating-cooling circulation, the equivalent hydraulic conductivity becomes asymptotic to a constant value, which implies there is no severe detachment of the pipe from the cement grout.

关键词： cement grout bentonite grout thermal conductivity workability equivalent permeability coefficient

Infrared-harvesting colloidal quantum dot inks for efficient photovoltaics: Impact of surface chemistry and device engineering

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Journal of Materials Science & Technology 2023年第16期147卷 224-240页

作者： Younghoon Kim min-Jae choi jongmin choi Department of Chemistry Kookmin UniversitySeoul02707Republic of Korea Department of Chemical and Biochemical Engineering Dongguk UniversitySeoul04620Republic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu42988Republic of Korea

Colloidal quantum dots(CQDs)are promising semiconducting materials,which can be used as a photoactive layer in various optoelectronic applications,because of their size-tunable bandgap energy,solution processability,and excellent optical and optoelectronic *** particular,these features have generated great interest in the development of CQD solar cells and led to a rapid increase in their power conversion *** improvements were enabled by many innovative approaches in terms of CQD’s surface chemistry and device architecture *** this review,a critical overview of the research progress in CQD solar cells is presented with a focus on the strategies adopted for achieving record efficiency in CQD solar *** strategies include the use of organic/inorganic surface ligands,pre-and post-treatment of CQDs,and solid-state/solution-phase ligand ***,we provide an understanding of the research history to inspire the rational design of next-generation CQD optoelectronic devices,such as solar cells,light-emitting diodes,and *** research on the development of infrared CQD solar cells as complementary platforms to other solar cell technologies is also critically discussed to provide another perspective on CQD technologies.

关键词： Quantum dot Lead sulfide Ligand exchange Colloidal ink Infrared light Solar cell

Effect of incision types for Artisan phakic intraocular lens implantation on ocular higher order aberrations

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International Journal of Ophthalmology(English edition) 2016年第12期9卷 1785-1789页

作者： Young min Park Bong Joon choi jong Soo Lee Department of Ophthalmology Gyeongsang National University School of Medicine Gyeongsang National University Changwon Hospital 11 Samjeongja-ro Seongsan-gu Changwon-si Gyeongsangnam-do 51472 Korea Lee Eye Clinic Pusan 47524 Korea Department of Ophthalmology School of Medicine Pusan National University and Medical Research Institute Pusan National University Hospital Pusan 602-739 Korea

AIM： To evaluate the effect of incision types for Artisan phakic intraocular lens （PIOL） implantation on ocular higher-order aberrations （HOAs）.METHODS： A retrospective review was conducted of the patients who had undergone Artisan PIOL implantation for the correction of myopia and followed up for at least 6mo. Patients are classified into 2 groups considering the incision type： cornea group with patients undergone clear corneal incision; sclera group with patients undergone sclera tunnel incision. All patients with postoperative astigmatism of under 1 diopter （D） were included to minimize the effect of residual astigmatism on postoperative HOAs. Visual acuity, special equivalents, astigmatism, predictability （±1 D from target refraction）, HOAs （coma, trefoil, spherical aberration）, and corneal endothelial counts were analyzed preoperatively and 6mo ***： At the postoperative 6mo, all patients of both groups achieved uncorrected visual acuity of 16/20 or better, and significantly decreased the spherical equivalents compared with preoperative values. The predictability of refractive correction was 96% in the former, and 94% in the latter. Unlike the sclera group, preoperative astigmatism decreased significantly in cornea group at postoperative 6mo. The HOAs increased significantly at postoperative 6mo compared to the preoperative values in both groups, and the root mean square （RMS） total and trefoil wavefront aberration of cornea group were significantly higher than those of sclera ***： Although corneal incision significantly reduces preexisting astigmatism, the postoperative 6mo of total RMS and trefoil aberration change may deteriorate the visual quality after Artisan PIOL implantation.

关键词： Artisan astigmatism higher-order aberrations incision phakic intraocular lens

Impacts of statin and metformin on neuropathy in patients with type 2 diabetes mellitus: Korean Health Insurance data

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World Journal of Clinical Cases 2021年第33期9卷 10198-10207页

作者： Hong Ki min Se Hee Kim jong Han choi Kyomin choi Hae-Rim Kim Sang-Heon Lee Department of Internal Medicine Konkuk University Medical CenterSeoul KS013South Korea Department of Neurology Konkuk University Medical CenterSeoul KS013South Korea Division of Rheumatology Department of Internal MedicineKonkuk University School of MedicineSeoul KS013South Korea

BACKGROUND Neuropathy is a common chronic complication in type 2 diabetes mellitus(T2DM).Statin and metformin are commonly used medications in T2DM patients,and some studies showed statin-or metformin-induced *** To evaluate the incidence of neuropathy among patients with T2DM associated with statin and metformin *** Korean Health Insurance Review and Assessment national patient sample data from 2016 and 2017 were *** with T2DM and no complications were divided into statin/metformin/statin+metformin users and *** incidence was defined by International Statistical Classification of Diseases and Related Health Problems,10th revision codes and concomitant prescriptions for anticonvulsants or *** regression analyses were conducted to examine the associations between statin/metformin/statin+metformin therapies and the incidence of *** score(PS)matching was performed on the basis of age,sex and *** Overall,34964 and 35887 patients with T2DM and no complications were included in the Korean Health Insurance Review and Assessment national patient sample datasets from 2016 and 2017,*** therapy was associated with increased risks of neuropathy in 2016 and 2017[PS-matched odds ratio(OR)=1.22,95%confidence interval(CI):1.08-1.38;PS-matched OR=1.17,95%CI:1.03-1.33,respectively].Metformin therapy was associated with reduced risks of neuropathy in 2016 and 2017(PS-matched OR=0.30,95%CI:0.21-0.42;PSmatched OR=0.44,95%CI:0.32-0.60,respectively).Combined statin+metformin therapy was not significantly associated with neuropathy in 2016 or 2017(PSmatched OR=0.85,95%CI:0.61-1.19;PS-matched OR=0.95,95%CI:0.66-1.38,respectively).CONCLUSION Statin therapy was associated with enhanced risk of new-onset neuropathy in patients with T2DM,but metformin therapy showed the opposite association.

关键词： Diabetes mellitus Neuropathies Hydroxymethylglutaryl-CoA reductase inhibitors Metformin

Effect of electrical stimulation on neural regeneration via the p38-RhoA and ERK1/2-Bcl-2 pathways in spinal cord-injured rats

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Neural Regeneration Research 2018年第2期13卷 340-346页

作者： min Cheol Joo Chul Hwan Jang jong Tae Park Seung Won choi Seungil Ro min Seob Kim Moon Young Lee Department of Rehabilitation Medicine and Institute of Wonkwang Medical Science School of Medicine Wonkwang University Department of Neurosurgery School of Medicine Wonkwang University Department of Anesthesiology and Pain Medicine School of Medicine Wonkwang University Department of Physiology and Cell Biology School of Medicine University of Nevada Department of Physiology and Institute of Wonkwang Medical Science School of Medicine Wonkwang University

Although electrical stimulation is therapeutically applied for neural regeneration in patients, it remains unclear how electrical stimulation exerts its effects at the molecular level on spinal cord injury （SCI）. To identify the signaling pathway involved in electrical stimulation improving the function of injured spinal cord, 21 female Sprague-Dawley rats were randomly assigned to three groups： control （no surgical intervention, n = 6）, SCI （SCI only, n = 5）, and electrical simulation （ES; SCI induction followed by ES treatment, n = 10）. A complete spinal cord transection was performed at the 10^th thoracic level. Electrical stimulation of the injured spinal cord region was applied for 4 hours per day for 7 days. On days 2 and 7 post SCI, the Touch-Test Sensory Evaluators and the Basso-Beattie-Bresnahan locomotor scale were used to evaluate rat sensory and motor function. Somatosensory-evoked potentials of the tibial nerve of a hind paw of the rat were measured to evaluate the electrophysiological function of injured spinal cord. Western blot analysis was performed to measure p38-RhoA and ERK1/2-Bcl-2 pathways related protein levels in the injured spinal cord. Rat sensory and motor functions were similar between SCI and ES groups. Com- pared with the SCI group, in the ES group, the latencies of the somatosensory-evoked potential of the tibial nerve of rats were significantly shortened, the amplitudes were significantly increased, RhoA protein level was significantly decreased, protein gene product 9.5 expression, ERK1/2, p38, and Bcl-2 protein levels in the spinal cord were significantly increased. These data suggest that ES can promote the recovery of electrophysiological function of the injured spinal cord through regulating p38-RhoA and ERK1/2-Bcl-2 pathway-related protein levels in the injured spinal cord.

关键词： Bcl-2 ERKI/2 p38 PGP9.5 RhoA spinal cord injury somatosensory evoked potential muscle contraction electrical impulses neural regeneration

Inverse correlation between gastroesophageal reflux disease and atrophic gastritis assessed by endoscopy and serology

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World Journal of Gastroenterology 2022年第8期28卷 853-867页

作者： Yoo min Han Su Jin Chung Seokha Yoo jong In Yang Ji min choi Jooyoung Lee Joo Sung Kim Department of Internal Medicine and Healthcare Research Institute Seoul National University Hospital Healthcare System Gangnam CenterSeoul 06236South Korea Department of Anesthesiology and Pain Medicine Seoul National University College of MedicineSeoul 03080South Korea Department of Internal Medicine and Liver Research Institute Seoul National University College of MedicineSeoul 03080South Korea

BACKGROUND Helicobacter pylori(***)infection is known to prevent the occurrence of gastroesophageal reflux disease(GERD)by inducing gastric mucosal ***,little is known about the relationship between atrophic gastritis(AG)and *** To confirm the inverse correlation between AG and the occurrence and severity of *** Individuals receiving health checkups who underwent upper gastrointestinal endoscopy at Seoul National University Healthcare System Gangnam Center were *** grade of reflux esophagitis was evaluated according to the Los Angeles *** AG(EAG)was categorized into six *** AG(SAG)was defined as pepsinogen I≤70 ng/m L and pepsinogen I/II ratio≤*** association between the extent of EAG and SAG and the occurrence and severity of GERD was evaluated using multivariate logistic regression *** In total,4684 individuals with GERD were compared with 21901 healthy *** multivariate logistic regression analysis,advanced age,male sex,body mass index>23 kg/m2,presence of metabolic syndrome,current smoking,and alcohol consumption were associated with an increased risk of *** for *** immunoglobulin G antibodies was associated with a decreased risk of *** was an inverse correlation between the extent of EAG and occurrence of GERD:Odds ratio(OR),1.01[95%confidence interval(CI):0.90-1.14]in C1,0.87(0.78-0.97)in C2,0.71(0.62-0.80)in C3,0.52(0.44-0.61)in O1,0.37(0.29-0.48)in O2,and 0.28(0.18-0.43)in ***,the extent of EAG showed an inverse correlation with the severity of *** presence of SAG was correlated with a reduced risk of GERD(OR=0.49,95%CI:0.28-0.87,P=0.014).CONCLUSION The extent of EAG and SAG exhibited strong inverse relationships with the occurrence and severity of *** followed by *** infection may be independently protect against GERD.

关键词： Gastroesophageal reflux disease Reflux esophagitis Helicobacter pylori Atrophic gastritis Pepsinogen

Parallel Cloth Simulation Using OpenGL Shading Language

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Computer Systems Science & Engineering 2022年第5期41卷 427-443页

作者： Hongly Va min-Hyung choi min Hong Department of Software Convergence Soonchunhyang UniversityAsan31538Korea Department of Computer Science and Engineering University of Colorado DenverDenverCO 80217USA Department of Computer Software Engineering Soonchunhyang UniversityAsan31538Korea

The primary goal of cloth simulation is to express object behavior in a realistic manner and achieve real-time performance by following the fundamental concept of *** general,the mass–spring system is applied to real-time cloth simulation with three types of ***,hard spring cloth simulation using the mass–spring system requires a small integration time-step in order to use a large stiffness ***,to obtain stable behavior,constraint enforcement is used instead of maintenance of the force of each *** force computation involves a large sparse linear solving *** to the large computation,we implement a cloth simulation using adaptive constraint activation and deactivation techniques that involve the mass-spring system and constraint enforcement method to prevent excessive elongation of *** the same time,when the length of the spring is stretched or compressed over a defined threshold,adaptive constraint activation and deactivation method deactivates the spring and generate the implicit *** method that uses a serial process of the Central Processing Unit(CPU)to solve the system in every frame cannot handle the complex structure of cloth model in *** simulation utilizes the Graphic Processing Unit(GPU)parallel processing with compute shader in OpenGL Shading Language(GLSL)to solve the system *** this paper,we design and implement parallel method for cloth simulation,and experiment on the performance and behavior comparison of the mass-spring system,constraint enforcement,and adaptive constraint activation and deactivation techniques the using GPU-based parallel method.

关键词： Adaptive constraint cloth simulation constraint enforcement GLSL compute shader mass–spring system parallel GPU

Real-time Volume Preserving Constraints for Volumetric Model on GPU

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Computers, Materials & Continua 2022年第10期73卷 831-848页

作者： Hongly Va min-Hyung choi min Hong Department of Software Convergence Soonchunhyang UniversityAsan31538Korea Department of Computer Science and Engineering University of Colorado DenverDenver80217COUSA Department of Computer Software Engineering Soonchunhyang UniversityAsan31538Korea

This paper presents a parallel method for simulating real-time 3D deformable objects using the volume preservation mass-spring system method on tetrahedron *** general,the conventional mass-spring system is manipulated as a force-driven method because it is fast,simple to implement,and the parameters can be ***,the springs in traditional mass-spring system can be excessively elongated which cause severe stability and robustness issues that lead to shape restoring,simulation blow-up,and huge volume loss of the deformable *** addition,traditional method that uses a serial process of the central processing unit(CPU)to solve the system in every frame cannot handle the complex structure of deformable object in ***,the first order implicit constraint enforcement for a mass-spring model is utilized to achieve accurate visual realism of deformable objects with tough constraint *** this paper,we applied the distance constraint and volume conservation constraints for each tetrahedron element to improve the stability of deformable object simulation using the mass-spring system and behave the same as its real-world *** reduce the computational complexity while ensuring stable simulation,we applied a method that utilizes OpenGL compute shader,a part of OpenGL Shading Language(GLSL)that executes on the graphic processing unit(GPU)to solve the numerical problems *** applied the proposed methods to experimental volumetric models,and volume percentages of all objects are *** average volume percentages of all models during the simulation using the mass-spring system,distance constraint,and the volume constraint method were 68.21%,89.64%,and 98.70%,*** proposed approaches are successfully applied to improve the stability of mass-spring system and the performance comparison from our experimental tests also shows that the GPU-based method is faster than CPU-based implementation for all cases.

关键词： Deformable object simulation mass-spring system implicit constraint enforcement volume conservation constraint GPU parallel computing

Enhanced thermoelectric composite performance from mesoporous carbon additives in a commercial Bi_(0.5)Sb_(1.5)Te_(3) matrix

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Journal of Materials Science & Technology 2021年第35期94卷 175-182页

作者： Seong-Tae Kim jong min Park Kwi-Il Park Sang-Eun Chun Ho Seong Lee Pyuck-Pa choi Seonghoon Yi School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology(KAIST)291 Daehak-roYuseong-guDaejeon 34141Republic of Korea

Composites were prepared,through hot pressing,using carbon materials with different pore size distributions as additives for commercial Bi_(0.5)Sb_(1.5)Te_(3) thermoelectric material(BST,p-type).Thermoelectric properties of the composites were measured in a temperature range of 298-473 *** conductivity of the composites,especially lattice thermal conductivity,was effectively decreased due to the mesoporous properties of the incorporated carbon *** electrical conductivity of the composites slightly decreased due to the electron scattering at the interface between the carbon material and the commercial BST *** composite with 0.2 vol.%mesoporous carbon powder(36%mesoporosity)exhibited a figure of merit value approximately 10.7%higher than that of commercial BST without *** behavior resulted in 116%improved output power in the composite block-based single element compared with a bare BST thermoelectric *** enhanced figure of merit was attributed to the effective reduction of lattice thermal conductivity by acoustic phonons scattering at the interface between the BST matrix and the mesoporous carbon as well as at the pore surfaces within the mesoporous *** utilizing mesoporous carbon materials used in this study,the shortcomings and economic difficulties of the composite process with low dimensional carbon additives(carbon nanotubes,graphene,and nanodiamond)can be overcome for extensive practical *** carbon powder with a tailored porosity distribution revealed the validity of bulk-type carbon additives to enhance the figure of merit of commercial thermoelectric materials.

关键词： Thermoelectric material Bi_(0.5)Sb_(1.5)Te_(3) Mesoporous carbon Lattice thermal conductivity Figure of merit