본 연구에서는 피식자의 flash display와 크기에 따른 생존율을 확인하였다. Flash display는 생물체가 가지는 방어 기작 중의 하나로, 피식자가 포식자로부터 도망을 갈 때, 예를 들어, 개구리 다리 안쪽의 색이 몸 색과 다른 경우나, 속날개의 색이 겉날개의 색과 다른 경우(ex. 뒷날개나방) 포식자에게 시각적으로 큰 혼란을 주어 생존율을 높이는 방어 기작 이다. 이를 연구하기 위해 visual studio enterprise 6.0프로그램으로 피식자의 크기와 색을 변경 가능 하게한 시뮬레이션을 만든 후 사람을 포식자로 설정하여 일반인 총 120명, 연령대는 10~50대 중 후반을 대상으로 실험 하였다. 실험 결과로 flash display를 사용하는 피식자의 생존율이 그렇지 않은 피식자 보다 높을 것으로 예상 하였고, 크기는 작을수록 더욱 유리 할 것으로 예측 하였다. 조사 결과 피식자의 크기와 색이 생존율과 상관관계에 있다는 것과 flash display 효과가 피식자의 생존율을 더욱 높여주었음을 발견하였다. 또한 flash display의 색이 주변 환경(이번 실험에서는 녹색 계통의 풀숲을 사용하였다.)과 확실하게 다른 색(녹색 계통의 색이 아닌 색)을 띄는 개체의 생존율이 flash display를 사용하지 않은 개체 보다 월등히 높았음을 확인하였다. 이는 Flash display가 피식자의 생존율을 높이는 요인이라는 것을 시사하고 있다.

New product crowdfunding has become an emerging method for start-ups to finance their innovative ideas. Since driving participants’ engagement is crucial to successful fundraising, it is important to study the factors that affect participants’ motivation to back the crowdfunding projects. In this paper, we first examine the impact of goal proximity on backing motivation and then we focus on investigating how group size affects perceived personal impact and resulting motivation to back a project. To test our hypotheses, we collected backing records and creativity ratings of smart wearables projects from a crowdfunding platform in China−Demohour.com. We used daily backers added as our dependent variable to capture potential backers’ motivation to back a project and modeled it using a negative binomial model with project and time fixed effects. Our empirical analyses suggest the following. First, consistent with existing research on the goal gradient effect, the funding ratio of a project is positively related to daily backers added while the positive effect becomes insignificant after reaching 100% funding ratio. Second, group size of backers has a negative effect on potential backers’ motivation. We explain that this is because individuals exert less effort due to decreased perceived personal impact when group size grows (social loafing effect) (Karau & Williams, 1993). Finally, creativity negatively moderates the effect of group size on backing motivation that the negative effect of group size especially calls for attention when the creativity level of the project is high.

In pressure retarded osmosis (PRO) process, thin film composite (TFC) type membranes which can withstand high operating pressure are required. In this study, glass fibers (GF) are used as additive for mechanical strength enhancement of the support layer of TFC membranes. The support layers were fabricated by a phase inversion method by using the casting solution of blended GF (two different size of milled GF) with polyethersulfone (PES). The fabricated support layers were characterized by FE-SEM, FT-IR, contact angle goniometer, and universal testing machine. Lab-scale ultrafiltration experiment was carried out to measure their performance. As a result, the support layer with milled GF showed higher mechanical strength and water flux than the pure PES support layer, and the support layer with smaller size GF showed higher performance.

목적: 근시안에서 소프트 콘택트렌즈를 이용하여 굴절교정을 한 후 조절자극에 따른 동공크기의 변화와 조절반응의 관계를 분석하였다. 방법: 평균연령 23.15 ±1.70세(20~28세)의 근시안 50명(100안)을 대상으로 하였으며, 검사실 조도 100 lx에서 동공크기는 나안상태와 소프트 콘택트렌즈로 굴절교정을 한 후 pupillometer를 사용하여 암소시, 어 두운 박명시, 밝은 박명시 상태에서 주시거리 3.5 m와 25 cm에서 측정하였다. 조절력은 푸쉬업검사(push up test), 조절반응은 개방형자동굴절력계를 사용하여 측정하였다. 조절자극에 의한 동공크기는 대응표본검 사(paired t-test)로 비교하였고, 동공변화량과 조절반응의 상관관계는 Pearson correlation으로 분석하였 으며, 유의수준은 p<0.05로 하였다. 결과: 근시안의 경우 소프트 콘택트렌즈로 굴절교정을 한 후 동공크기는 감소하였고(p<0.05), 조절자극 에 의해 동공크기 감소량이 많을수록 양안 및 단안의 조절반응은 작아졌다(p<0.05). 그러나 조절자극에 의 해 동공크기가 변하지 않는 대상자는 조도에 따라 35~37%를 차지하였으며, 산동 된 경우도 7~11%로 나타 났다. 조절자극에 의해 축동된 그룹의 조절반응값은 동공크기의 변화가 없거나 산동 된 그룹의 조절반응 값 보다 작은 것으로 나타났다(p<0.05). 결론: 소프트 콘택트렌즈로 교정한 근시안의 경우 조절자극에 의해 동공크기가 감소하며 이에 따라 조절 반응이 감소하였으나, 동공이 축동되지 않은 경우에는 축동된 그룹보다 조절반응이 크게 측정되었다. 본 연 구결과는 콘택트렌즈 착용 후 근거리 작업 시 나타나는 안정피로를 이해하고 멀티포컬 콘택트렌즈 착용 후 나타나는 시기능을 이해하는 기초자료가 될 것으로 생각된다.

This study was carried out to investigate the effect of grain size on the damping capacity of the Fe-26Mn-4Co-2Al damping alloy. α’ and ε-martensite were formed by cold working, and these martensites were formed with a specific direction and surface relief. With an increase in grain size, the volume fraction of α’ and ε-martensite increased by decrement the austenite phase stability. This volume fraction more rapidly increased in cold-rolled specimen than in the specimen that was not cold-rolled. The damping capacity also increased more with the augmentation an increased grain size and more rapidly increased in cold-rolled specimen than in the specimen that was not cold rolled. The effect of grain size on the damping capacity was larger in the cold-rolled specimen than the specimen that was not cold-rolled. Damping capacity linearly increased with an increase in volume fraction of ε-martensite. Thus, the damping capacity was affected by the ε-martensite.

This study aimed to investigate the effect of smartphone size and use on fatigue of the extensor pollicis longus and abductor digiti minimi, and digiti minimi deformity. The 40 people assigned to the experimental group spent at least 6 hours using the smartphone and used the digiti minimi for support. The control group spent at least 3 hours using the smartphone, however did not use digiti mini for support. Questionnaires were used to measure smartphone usage, daily use duration, and method of holding the smartphone device. X-rays of distal interphalangeal joint angle deformity of the digiti minimi were assessed. Surface electromyography was used to analyze muscle fatigue. The angle deformity was significantly different between the experimental group and the control group, and fatigue of the extensor pollicis longus and abductor digiti minimi of the large smartphone users were high. The muscle fatigue was reduced when the smartphone size fit well with the user's hand. This study suggests that the size of the smartphone influence the fatigue of the hand muscles.

SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

The effect of the mixing method on the characteristics of hybrid-structure W powder with nano and micro sizes is investigated. Fine WO3 powders with sizes of ~0.6 μm, prepared by ball milling for 10 h, are mixed with pure W powder with sizes of 12 μm by various mixing process. In the case of simple mixing with ball-milled WO3 and micro sized W powders, WO3 particles are locally present in the form of agglomerates in the surface of large W powders, but in the case of ball milling, a relatively uniform distribution of WO3 particles is exhibited. The microstructural observation reveals that the ball milled WO3 powder, heat-treated at 750oC for 1 h in a hydrogen atmosphere, is fine W particles of ~200 nm or less. The powder mixture prepared by simple mixing and hydrogen reduction exhibits the formation of coarse W particles with agglomeration of the micro sized W powder on the surface. Conversely, in the powder mixture fabricated by ball milling and hydrogen reduction, a uniform distribution of fine W particles forming nano-micro sized hybrid structure is observed.

Recycled cenosphere, which is a hollow shaped particle from fly ash, has become attractive as a building material due to its light weight and excellent heat insulation and soundproof properties. In this paper, we investigated the effect of cenosphere size on the physical and optical properties. High brightness of cenosphere as raw material is required for a wide range of ceramics applications, particularly in fields of building materials and industrial ceramic tiles. Cenospheres were sorted by particle size; the microstructure was analyzed according to the cenosphere size distribution. Cenospheres were generally composed of quartz, mullite, and amorphous phase. Colour measurement corresponding to chemical composition revealed that the contents of iron oxide and carbon in the cenospheres were the major factors determining the brightness of the cenospheres.

The red ginseng is known to have effects on antioxidativity and cytotoxicity. Nanoscale active substances have various advantages such as improved bioavailability and permeation ability into the cell. However, few studies conducted with the nanoparticles of red ginseng due to its low yield rate and difficulty of manufacturing the product in pilot scale. This study, therefore, investigated the size effects of ultra-fine powder of red ginseng on antioxidativity and cytotoxicity. Red ginseng powder (6, 8, or 158 μm) prepared using a pilot scale was provided by a local company. Antioxidativity was measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays, and cytotoxicity was tested by methylthiazolyl tetrazolium (MTT) assay. The results of DPPH and ABTS radical electron donating ability IC50 of red ginseng were ranged from 2.27 to 3.34 mg/ml and 2.94 to 3.09 mg/ml, respectively, which were not significantly different between all samples. However, the results of cytotoxicity clearly showed a pattern of decreased toxicity in 6 and 8 μm power compared to 158 μm powder. Unexpectedly, particle sizes of red ginseng did not significantly affect antioxidativity. It is believed that these were related to the process of pilot scale production. These phenomena are also believed to be caused by aggregation of low size power particle that increases water holding capacity. From our result, it is concluded that this range of particle size of red ginseng affected the reduction of cytotoxicity.

목 적: 담배 흡연이 동공크기, 시력, 조절력 및 눈물막에 미치는 급성 및 만성효과를 확인하고자 하였다. 방 법: 성인 남성 중 비흡연자 30명, 흡연자 25명의 지원자를 대상으로 하였다. 흡연의 급성효과를 관찰 하기 위하여 흡연자에게는 0.5 mg의 니코틴이 함유된 동일한 담배 1 개비를 피우도록 하고 흡연 직후 명소 시와 박명시 상태에서 동공크기, 대비시력, 대비감도, 고위수차, 조절력 및 눈물막안정성을 측정하였다. 동 공크기는 동공측정계(VIP™-200 Pupillometer)로, 안구수차는 파면수차계(KR-1W)를 사용하여 4 ㎜ 동공 크기에서 측정하였으며, 100%와 10% 대비시력, 대비감도를 측정하고, 조절력은 Push-up test 검사로, 눈 물막 안정성은 눈물막파괴시간(TBUT)을 측정하여 흡연 전과 비교하였다. 만성효과는 비흡연자와 흡연자의 흡연 전 상태에서 측정한 결과값을 비교하였다. 결 과: 흡연의 급성효과로 동공크기는 조도와 휘도에 상관없이 모두 유의하게 감소하였으며(p<0.05), 명 소시와 박명시에서 측정한 저대비 시력은 유의하게 향상되었다(p<0.05). 대비감도와 고위수차는 차이가 없 었고(p>0.05), 흡연 후 조절력과 TBUT는 유의하게 감소하였다(p<0.05). 흡연자와 비흡연자의 동공크기는 모든 조도와 휘도에서 차이가 없었고, 대비시력, 대비감도, 고위수차, 조절력 및 TBUT도 유의한 차이가 관 찰되지 않았다. 결 론: 흡연의 급성효과로 동공이 축동되고, 조절력 및 눈물막 안정성이 감소하며, 저대비 시력이 향상되 었다. 그러나 흡연은 만성적으로 동공크기, 시력, 조절력 및 눈물안정성에 영향을 주지 않는 것으로 나타나 흡연은 일시적으로 시기능에 영향을 주는 것으로 생각된다.

하수오(Polygonum multiflorum Thunb.)는 여뀌과에 속하는 초본식물로 동아시아와 북아메리카에 자생하고 있다. 하수오는 관상용으로도 이용되며, 한의학에서 뿌리를 약용으로 사용한다. 하지만 월동 이 어렵고 노동력 소모가 많아 최근 재배농가가 감소하고 있다. 본 연구에서는 하수오의 우량종묘를 짧 은 시간에 대량생산하기 위하여 수경재배에 적합한 양액과 조직배양묘의 크기를 조사하였다. 토양에 적 응이 완료된 하수오 종묘는 크기에 따라 Type 1, Type 2 및 Type 3으로 나누어 4종류의 양액에 치상 하였다. 치상 후 양액과 종묘에 따른 생육차이를 확인하기 위하여 생육조사를 실시하였다. 생육조사는 8주 동안 양액에서 생육시킨 후 줄기길이, 잎 수, 마른 잎 수, 줄기 수, 생체중과 건물중에 대해 측정 하였다. 그 결과 양액3에서 Type 1과 Type 2의 뿌리길이는 각각 33.8cm와 29.5cm로 각각 나타났다. 이와 유사한 경향으로 덩굴 길이도 CaCl2가 첨가 된 양액3에서 Type 1과 Type 2가 가장 길게 나타나 우수한 생육을 보였다. 이처럼 뿌리가 증대된 종묘는 밭으로 이식 될 때 활착을 도와 우수한 초기생육 을 나타낼 것이라 사료된다. 반면 Type 3는 잎끝마름과 고사하는 현상을 보여 추후 양액의 적정농도에 대한 추가 실험이 필요할 것이라 사료된다.

The purpose of this study is to find out the effect of particle size of sediment on adsorption of fluoride. Particle size is classified as sand, silt and clay. Adsorption equilibrium time, adsorption isotherms and the effect of pH were investigated through batch tests. The pHpzc of sand, silt, clay was respectively 6, 8, 4.5 and AEC (anion exchange capacity) was highest in silt, respectively 0.0095, 0.0224, 0.014 meq g-1. Adsorption of fluoride on the sediment was in equilibrium within 300 minutes from all particle size. The experimental data of isotherms at various pH were well explained by Freundlich equation. As the experimental results of the effect of pH, the adsorption efficiency of sand and silt were reduced after the pHpzc. However, the adsorption efficiency of clay was maintained after the pHpzc, and decreased rapidly higher than pH 12.

This study investigates the thermal shock property of a polycrystalline diamond compact (PDC) produced by a high-pressure, high-temperature (HPHT) sintering process. Three kinds of PDCs are manufactured by the HPHT sintering process using different particle sizes of the initial diamond powders: 8-16 μm (D50 = 4.3 μm), 10-20 μm (D50 = 6.92 μm), and 12-22 μm (D50 = 8.94 μm). The microstructure observation results for the manufactured PDCs reveal that elemental Co and W are present along the interface of the diamond particles. The fractions of Co and WC in the PDC increase as the initial particle size decreases. The manufactured PDCs are subjected to thermal shock tests at two temperatures of 780oC and 830oC. The results reveal that the PDC with a smaller particle size of diamond easily produces microscale thermal cracks. This is mainly because of the abundant presence of Co and WC phases along the diamond interface and the easy formation of Co-based (CoO, Co3O4) and W-based (WO2) oxides in the PDC using smaller diamond particles. The microstructural factors for controlling the thermal shock property of PDC material are also discussed.

본 연구에서는 입자크기가 다른 3가지 α-알루미나 분체로부터 주입성형법과 소결법을 혼용하여 튜브형 α-알루 미나 지지체를 제조하여 초기 α-알루미나 분체의 입자크기와 소결 온도가 지지체의 기공구조와 기체투과 특성에 미치는 영 향을 고찰하였다. 평균입경이 0.2, 0.5, 1.7 μm인 α-알루미나 분체를 사용했을 시 제조된 α-알루미나 지지체는 각각 약 80, 130, 200 nm의 평균 기공경을 가졌으며 평균 기공경은 소결 온도 보다는 초기 알루미나 분체의 입자크기에 의존하였다. 모 든 시편에서 소결 온도가 증가할수록 지지체의 부피 밀도는 증가하였고 겉보기 기공률은 감소하였다. He, N2, O2, CO2에 대 하여 30°C에서 단일기체 투과 특성을 평가한 결과, 기체 투과도는 기공경 제곱에 비례하여 증가하였고 기공률이 증가함에 따 라서 직선적으로 증가하였다. 이를 토대로 제조된 α-알루미나 지지체의 기체 투과는 점성유동(viscous flow)에 의하여 이루 어지며, α-알루미나 지지체의 기체 투과 특성은 초기 α-알루미나 분체의 입자크기와 소결온도를 제어함으로써 조절될 수 있 음을 확인할 수 있었다.

This paper presents a study of the tensile properties of austenitic high-manganese steel specimens with different grain sizes. Although the stacking fault energy, calculated using a modified thermodynamic model, slightly decreased with increasing grain size, it was found to vary in a range of 23.4 mJ/m2 to 27.1 mJ/m2. Room-temperature tensile test results indicated that the yield and tensile strengths increased; the ductility also improved as the grain size decreased. The increase in the yield and tensile strengths was primarily attributed to the occurrence of mechanical twinning, as well as to the grain refinement effect. On the other hand, the improvement of the ductility is because the formation of deformation-induced martensite is suppressed in the high-manganese steel specimen with small grain size during tensile testing. The deformationinduced martensite transformation resulting from the increased grain size can be explained by the decrease in stacking fault energy or in shear stress required to generate deformation-induced martensite transformation.

P-type ternary Bi0.5Sb1.5Te3 alloys are fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Different ball sizes are used in the MA process, and their effect on the microstructure; hardness, and thermoelectric properties of the p-type BiSbTe alloys are investigated. The phases of milled powders and bulks are identified using an X-ray diffraction technique. The morphology of milled powders and fracture surface of compacted samples are examined using scanning electron microscopy. The morphology, phase, and grain structures of the samples are not altered by the use of different ball sizes in the MA process. Measurements of the thermoelectric (TE) transport properties including the electrical conductivity, Seebeck coefficient, and power factor are measured at temperatures of 300- 400 K for samples treated by SPS. The TE properties do not depend on the ball size used in the MA process.