• Science of Emotion and Sensibility
• /
• v.23 no.2
• /
• pp.51-60
• /
• 2020

This study aimed to develop a modular smart clothing system for heart rate monitoring that reduces the inconvenience caused by battery charging and the large size of measurement devices. The heart rate monitoring system was modularized into a temporary device and a continuous device to enable heart rate monitoring depending on the requirement. The temporary device with near-field communication (NFC) and heart rate sensors was developed as a clothing attachment type that enables heart rate monitoring via smart phone tagging when required. The continuous device is based on Bluetooth Low Energy (BLE) communication and batteries and was developed to enable continuous heart rate measurement via a direct connection to the temporary device. Furthermore, the temporary device was configured to connect with a textile electrode made of a silver-based knitted fabric designed to be located below the pectoralis major muscle for heart rate measurement. Considering the user-experience factors, key functions, and the ease of use, we developed an application to automatically log through smart phone tagging to improve usability. To evaluate the accuracy of the heart rate measurement, we recorded the heart rate of 10 healthy male subjects with a modular smart clothing system and compared the results with the heart rate values measured by the Polar RS800. Consequently, the average heart rate value measured by the temporary system was 85.37, while that measured by the reference device was 87.03, corresponding to an accuracy of 96.73%. No significant difference was found in comparison with the reference device (T value = -1.892, p = .091). Similarly, the average heart rate measured by the continuous system was 86.00, while that measured by the reference device was 86.97, corresponding to an accuracy of 97.16%. No significant difference was found in terms of the heart rate value between the two signals (T value = 1.089, p = .304). The significance of this study is to develop and validate a modular clothing system that can measure heart rates according to the purpose of the user. The developed modular smart clothing system for heart rate monitoring enables dual product planning by reducing the price increase due to unnecessary functions.

• Journal of the Korean Electrochemical Society
• /
• v.20 no.4
• /
• pp.67-74
• /
• 2017

Layered Ni-rich NCM cathode materials $Li[Ni_xCo_{(1-x)/2}Mn_{(1-x)/2}]O_2$ ($x{\geq}0.6$) have advantages of high energy density and cost competitive over $LiCoO_2$. The discharge capacity of NCM increases proportionally to the Ni contents. However, there is a problem that it is difficult to realize the stable electrochemical performance due to cation mixing. In this study, synthesis conditions for the layered Ni-rich NCMs are investigated to achieve deliver the ones having good electrochemical performances. Synthesis parameters are atmosphere, lithium source, synthesis time, synthesis temperature and Li/M (M=transition metal) ratio. The degree of cation mixing gets worse as the Ni content is increased from $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ (NCM6) to $Li[Ni_{0.8}Co_{0.1}Mn_{0.1}]O_2$ (NCM8). It is confirmed that higher level of cation mixing affects negatively on the electrochemical performance of NCMs. Optimum synthesis conditions are explored for NCMx (x=6, 7, 8) in order to reduce the cation mixing. Under optimized conditions for three representative NCMx, a high initial discharge capacity and a good cycle life are obtained for $180mAh{\cdot}g^{-1}$, 96.2% (50 cycle) in NCM6, $187mAh{\cdot}g^{-1}$, 94.7% (50 cycle) in NCM7, and $201mAh{\cdot}g^{-1}$, 92.7% (50 cycle) in NCM8, respectively.

• Journal of the Korean Electrochemical Society
• /
• v.20 no.1
• /
• pp.7-12
• /
• 2017

Using a precursor of $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ as a starting material, a surface-modified cathode material was obtained by coating with KCl, where the added KCl reduces residual Li compounds such as $Li_2CO_3$ and LiOH, on the surface. The resulting electrochemical properties were investigated. The amounts of $Li_2CO_3$ and LiOH decreased from 8,464 ppm to 1,639 ppm and from 8,088 ppm to 6,287 ppm, respectively, with 1 wt% KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ that had been calcined at $800^{\circ}C$. X-ray diffraction results revealed that 1 wt% of KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ did not affect the parent structure but enhanced the development of hexagonal crystallites. Additionally, the charge transfer resistance ($R_{ct}$) decreased dramatically from $225{\Omega}$ to $99{\Omega}$, and the discharge capacity increased to 182.73mAh/g. Using atomic force microscopy, we observed that the surface area decreased by half because of the exothermic heat released by the Li residues. The reduced surface area protects the cathode material from reacting with the electrolyte and hinders the development of a solid electrolyte interphase (SEI) film on the surface of the oxide particles. Finally, we found that the introduction of KCl into $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ is a very effective method of enhancing the electrochemical properties of this active material by reducing the residual Li. To the best of our knowledge, this report is the first to demonstrate this phenomenon.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.10 no.2
• /
• pp.157-165
• /
• 2007

Purpose: Ingested foreign bodies are removed by endoscopy, surgery or spontaneous passage, however, the decision of therapeutic modality chosen depends on the type, size, shape and location of the ingested foreign bodies. Therefore, this study was conducted to investigate the rate and characteristics of foreign bodies that were passed spontaneously out of the intestine. Methods: One hundred and sixty patients who visited Samsung Medical Center for treatment of gastrointestinal foreign bodies between January 2001 to July 2007 were enrolled in this study. Related data was colleted by reviewing the medical records of patients with proven foreign bodies retrospectively, as well as by conducting phone interviews with the parents of the patients. All cases were classified based on the nature and location of the ingested foreign body, as well as whether it was treated by spontaneous passage. Results: Of the 160 cases involving the passage of foreign bodies in children were included in this study (95 boys and 65 girls), endoscopic removals, operative removals or spontaneous passages were conducted in 80, 3 and 77 patients, respectively. The spontaneous passage rates for each type of object were as follows; coins (36.5%), bead and baduk stones (83.3%), long and sharp materials (52.6%), magnets (69.2%) and disc batteries (50.0%). In cases involving round-shaped foreign bodies, such as coins, the diverse spontaneous passage rates were more diverse. When foreign bodies were stuck below esophagus, similar sized coins and baduk stones had spontaneous passage rates greater than 80% regardless of age. Conclusion: It is better for clinicians to wait for spontaneous passage to occur in cases involving coins or round-shaped foreign bodies that are located at or below the stomach.

• Clinical and Experimental Pediatrics
• /
• v.50 no.2
• /
• pp.138-142
• /
• 2007

Purpose : The purpose of this study is to find out the changing pattern of drug or foreign body ingestion between 1990s and 2000s in Wonju Christian Hospital, which is located in one of the most rapidly urbanizing cities in Korea. Methods : We retrospectively reviewed the medical records of patients with acute drug intoxication and foreign body ingestion from January 1991 to December 1994 and from January 2001 to December 2004. We performed clinical analysis and compared the results of the 1990s and 2000s. Results : There were 43 cases of acute drug intoxication in the 1990s, and 35 cases in the 2000s. Foreign body ingestion was 47 cases in the 1990s and 22 cases in the 2000s. The ingested foreign bodies were chiefly coins (46.8 percent), Weiqi chips (14.9 percent), plastic toys (6.4 percent) and others (31.9 percent) in the 1990s. In the 2000s, others (58.2 percent) were the most commonly ingested foreign body with mercury batteries (23.8 percent), nails (9 percent), pins (9 percent) following. The most common cause of drug intoxication was medical drugs (37.2 percent) others (23.2 percent), agricultural agents (13.9 percent), carbon monoxide (11.6 percent), rodenticide (9.3 percent), insecticide (9.3 percent) in the 1990s. In the 2000s the most common causes were others (34.3 percent), medical drug (31.4 percent), agriculture agents (20 percent), detergent (11.4 percent), insecticide (2.9 percent) and carbon monoxide (2.9 percent). The highest incidence age group was the 1-3 year old group, both in acute drug intoxication and foreign body ingestion. There were no changes in the incidence age group between the 1990s and the 2000s. Conclusion : There were some significant changes in the cause of acute drug intoxication and foreign body ingestion between the 1990s and 2000s. New education programs for preventing acute drug intoxication and foreign body ingestion are important and necessary.

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.75-82
• /
• 2019

Flexible solar cells have attracted enormous attention in recent years due to their wide applications such as portable batteries, wearable devices, robotics, drones, and airplanes. In particular, the demands of the flexible silicon and compound semiconductor solar cells with high efficiency and high reliability keep increasing. In this study, we fabricated a flexible InGaP/GaAs double-junction solar module. Then, the effects of the wind speed and ambient temperature on the operating temperature of the solar cell were analyzed with the numerical simulation. The temperature distributions of the solar modules were analyzed for three different wind speeds of 0 m/s, 2.5 m/s, and 5 m/s, and two different ambient temperature conditions of 25℃ and 33℃. The flexibility of the flexible solar module was also evaluated with the bending tests and numerical bending simulation. When the wind speed was 0 m/s at 25 ℃, the maximum temperature of the solar cell was reached to be 149.7℃. When the wind speed was increased to 2.5 m/s, the temperature of the solar cell was reduced to 66.2℃. In case of the wind speed of 5 m/s, the temperature of the solar cell dropped sharply to 48.3℃. Ambient temperature also influenced the operating temperature of the solar cell. When the ambient temperature increased to 33℃ at 2.5 m/s, the temperature of the solar cell slightly increased to 74.2℃ indicating that the most important parameter affecting the temperature of the solar cell was heat dissipation due to wind speed. Since the maximum temperatures of the solar cell are lower than the glass transition temperatures of the materials used, the chances of thermal deformation and degradation of the module will be very low. The flexible solar module can be bent to a bending radius of 7 mm showing relatively good bending capability. Neutral plane analysis was also indicated that the flexibility of the solar module can be further improved by locating the solar cell in the neutral plane.

• Clean Technology
• /
• v.24 no.1
• /
• pp.77-84
• /
• 2018

In this study, $Li_4Ti_5O_{12}$ anode materials for lithium ion battery were synthesized by dry ball-mill method. Polyvinyl chloride (PVC) as a carbon source was added to improve electrochemical properties. When the PVC was added after $Li_4Ti_5O_{12}$ formation, the spinel structure was well synthesized and it was confirmed by X-ray diffraction (XRD) experiments. When the carbon material was added before the synthesis and the heat treatment was performed, it was confirmed that a material having a different crystal structure was synthesized even when a small amount of carbon material was added. In the case of $Li_4Ti_5O_{12}$ without the carbon material, the electrical conductivity value was about $10{\mu}S\;m^{-1}$, which was very small and similar to that of the nonconductor. As the carbon was added, the electrical conductivity was greatly improved and increased up to 10,000 times. Electrochemical impedance spectroscopy (EIS) analysis showed that the size of semicircle corresponding to the resistance decreased with the carbon addition. This indicates that the resistance inside the electrode is reduced. According to the Cyclic voltammetry (CV) analysis, the potential difference between the oxidation peak and the reduction peak was reduced with carbon addition. This means that the rate of lithium ion insertion and deinsertion was increased. $Li_4Ti_5O_{12}$ with 9.5 wt% PVC added sample showed the best properties in rate capabilities of $180mA\;h\;g^{-1}$ at 0.2 C-rate, $165mA\;h\;g^{-1}$ at 0.5 C-rate, and $95.8mA\;h\;g^{-1}$ at 5 C-rate.

• Korean Journal of Poultry Science
• /
• v.16 no.3
• /
• pp.149-156
• /
• 1989

Two broiler experiments were carried out to determine whether supplementation of zeolite in the diet would affect broiler performance and economical efficiency. Day old male broiler chickens of Abor Acres strain were used. In the first experiment,60 birds were distributed into f groups of 10 birds each. Three groups of chickens were randomly placed on one of the following single-stage (0-6wks) experimental diets； control diet (non-supplemented) or 2% zeolite supplemented diet (supplemented to the control). In the second experiment,216 birds were distributed into 24 groups of 9 birds each. Eight groups of chickens were randomly placed on one of the 3 two-stage diet (starter；0-4wks, finisher；5-7wks)；control diet ($T_1$ , non-supplemented), 2% zeolite diet ($T_2$：isocaloric and isonitrogenous as $T_1$ ) and 2% zeolite supplemented diet ($T_3$, supplemented to the control). Birds were housed in the batteries, and feeds and water were fed ad libitum. The results of Experiment 1 showed that birds fed control diet were heavier than those fed 2% zeolite supplemented diet up to 4th wks of age. However, birds fed the latter grew more at 5th and 6th wk. Overall weight gain, feed intake and feed efficiency were not significantly different. The results of Experiment 2 showed that there were no significant differences in weight gains, feed intakes and feed efficiencies among treatments during starter, finisher to overall period. The moisture levels in excreta of the birds were significantly (P＜0.01) less when zeolite was included in the diets and those in excreta significantly (P ＜ 0.01) increased as the ambient temperature increased. Economical efficiency expressed in fed cost (won) required per kg weight gin were 346.55 (T$_3$),348.34 ($T_1$ ) and 359.85 ($T_2$).

• Journal of the Korean Electrochemical Society
• /
• v.22 no.3
• /
• pp.128-137
• /
• 2019

A lithium is the lightest metal on the earth. It has some attractive characteristics as a negative electrode material such as a low reduction potential (-3.04 V vs. SHE) and a high theoretical capacity ($3,860mAh\;g^{-1}$). Therefore, it has been studied as a next generation anode material for high energy lithium batteries. The thin lithium electrode is required to maximize the efficiency and energy density of the battery, but the physical roll-press method has a limitation in manufacturing thin lithium. In this study, thin lithium electrode was fabricated by electrodeposition under various conditions such as compositions of electrolytes and the current density. Deposited lithium showed strong relationship between process condition and its characteristics. The concentration of electrolyte affects to the shape of deposited lithium particle. As the concentration increases, the shape of particle changes from a sharp edged long one to a rounded lump. The former shape is favorable for suppressing dendrite formation and the elec-trode shows good stripping efficiency of 92.68% (3M LiFSI in DME, $0.4mA\;cm^{-2}$). The shape of deposited particle also affected by the applied current density. When the amount of current applied gets larger the shape changes to the sharp edged long one like the case of the low concentration electrolyte. The combination of salts and solvents, 1.5M LiFSI + 1.5M LiTFSI in DME : DOL [1 : 1 vol%] (Du-Co), was applied to the electrolyte for the lithium deposition. The lithium electrode obtained from this electrolyte composition shows the best stripping efficiency (97.26%) and the stable reversibility. This is presumed to be due to the stability of the surface film induced by the Li-F component and the DOL effect of providing film flexibility.

• Journal of the Korean Electrochemical Society
• /
• v.24 no.3
• /
• pp.52-64
• /
• 2021

The effect of Fe and BO₃ doping on structure, thermal, and electrical properties of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y (x = 0.2, 0.5)-based glass and glass ceramics was investigated. In addition, their crystallization behavior during sintering and ionic conductivity were also investigated in terms of sintering temperature. FT-IR and XPS results indicated that Fe²⁺ and Fe³⁺ ions in Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass worked as a network modifier (FeO₆ octahedra) and also as a network former (FeO₄ tetrahedra). In the case of the glass with low substitution of BO₃, boron formed (PB)O₄ network structure, while boron preferred BO₃ triangles or B₃O₃ boroxol rings with increasing the BO₃ content owing to boic oxide anomaly, which can result in an increased non-bridging oxygen. The glass transition temperature (GTT) and crystallization temperature (CT) was lowered as the BO₃ substitution was increased, while Fe²⁺ lowered the GTT and raised the CT. The ionic conductivity of Li_1+xFe_xTi_2-x(PO₄)_3-y(BO₃)_y glass ceramics were 8.85×10^-4 and 1.38×10^-4S/cm for x = 0.2 and 0.5, respectively. The oxidation state of doped Fe and boric oxide anomaly were due to the enhanced lithium ion conductivity of glass ceramics.