응력부식귀열

Boyd, Walter K. 대한금속재료학회(대한금속학회) 1969 대한금속·재료학회지 Vol.6 No.4

응력부식균열은 입계균열(粒界龜裂) 또는 입내균열(粒內龜裂)도 진행된다. 응력부식 균열은 작용된 역학적 응력이나 잔류응력이 부식작용과 결합하여 자연적으로 일어나는 균열현상을 말한다. 일반으로 순수한 금속은 응력부식균열을 잘 받지 않으나, 미량의 불순물이 혼입된 금속이나 합금은 균열을 쉽게 받게 된다. 예컨데 구리에 40ppm의 인(P)이 혼입할 때는 균열을 받기 쉽다. 이 균열의 기구에 대해서는 아직도 여러가지 학설이 있으나, 주로 기계학적 요소와 전기학적 요소가 결합됨으로서 이루어진다고 본다. 이런 응력부식균열을 막기 위해서는 위험한 응력을 제거할 것, 부식환경을 조절할 것, 및 재질을 대치할 것 등을 들 수 있다. Stress corrosion cracking is perhaps the most insidious of all forms of corrosion. It may develop as very fine intergranular or transgranular cracks, with little or no telltale evidence of corrosion products. In fact in many instances there may be no macroscopic indication of impending failure. Stress corrosion cracking map be defined as the spontaneous failure of a metal as a result of the combined effects of corrosion and static stress either residual or applied. The result is a brittle fracture in an otherwise ductile material. It is generally accepted that pure metals are immune to stress corrosion cracking. However, even a few parts per million of impurities may render the metal or alloy susceptible to cracking. The mechanism of cracking is not completely understood. Theories range from purely mechanical to electrochemical. The fact that propagating cracks can be stopped by the application of cathodic protection or accelerated by anodic currents suggests that the initiation and propagation of cracks involve at least in part an electrochemical process. The principle means of eliminating or reducing the occurrence of stress corrosion cracking are: (1) The reduction or elimination of dangerous tensile stresses. (2) The alteration of the environment to render it less dangerous. (3) The replacement of the alloy with another that is not susceptible to stress corrosion cracking.

Cryptography in the Cloud: Advances and Challenges

Boyd, Colin The Korea Institute of Information and Commucation 2013 Journal of information and communication convergen Vol.11 No.1

Cloud computing is a currently developing revolution in information technology that is disturbing the way that individuals and corporate entities operate while enabling new distributed services that have not existed before. At the foundation of cloud computing is the broader concept of converged infrastructure and shared services. Security is often said to be a major concern of users considering migration to cloud computing. This article examines some of these security concerns and surveys recent research efforts in cryptography to provide new technical mechanisms suitable for the new scenarios of cloud computing. We consider techniques such as homomorphic encryption, searchable encryption, proofs of storage, and proofs of location. These techniques allow cloud computing users to benefit from cloud server processing capabilities while keeping their data encrypted; and to check independently the integrity and location of their data. Overall we are interested in how users may be able to maintain and verify their own security without having to rely on the trust of the cloud provider.

HOLOMORPHIC FUNCTIONS AND THE BB-PROPERTY ON PRODUCT SPACES

Boyd, Christopher Korean Mathematical Society 2004 대한수학회지 Vol.41 No.1

In [25] Taskinen shows that if $\{E_n\}_n\;and\;\{F_n\}_n$ are two sequences of Frechet spaces such that ($E_m,\;F_n$) has the BB-property for all m and n then (${\Pi}_m\;E_m,\;{\Pi}_n\;F_n$) also has the ΒΒ-property. Here we investigate when this result extends to (i) arbitrary products of Frechet spaces, (ii) countable products of DFN spaces, (iii) countable direct sums of Frechet nuclear spaces. We also look at topologies properties of ($H(U),\;\tau$) for U balanced open in a product of Frechet spaces and $\tau\;=\;{\tau}_o,\;{\tau}_{\omega}\;or\;{\tau}_{\delta}$.

Effect of LED Wavelength on Growth and Production of Astaxanthinin Haematococcus Pluvialis

( Boyd Warren ),( Ki An Kim ),( Sang Ho Chun ),( Tae-hawn Oh ),( Woo-hyuk Jung ),( Kyoo Jin Jung ),( Sung-kun Yim ) 한국키틴키토산학회 2020 한국키틴키토산학회지 Vol.25 No.3

Biomass production and astaxanthin accumulation in Haematococcus pluvialis were investigated under different light-emitting diode (LED) wavelengths. The maximum biomass (5.41 and 6.25 g dry weight/L) was obtained under the red LEDs (630 nm and 660 nm) with light intensity of 200 μmol m^-2s^-1 at day 7 after cultivation in mixotrophic media with modified Bold’s Basal Medium including sodium acetate. The highest astaxanthin content (31.4 mg/g dry weight biomass) was accumulated when incubated under red LEDs (630 nm) for 4 days by increasing the light intensity to 1,000 μmol m^-2s^-1. In these results, we propose an efficient way of cultivating H. pluvialis in mixotrophic media under red (630 nm) LEDs for maximum biomass production and then increasing the light intensity over 1,000 μmol m-2s-1 to induce a high level of astaxanthin content.

Recent Advances in Amino Acid and Energy Nutrition of Prolific Sows - Review -

Boyd, R.D.,Touchette, K.J.,Castro, G.C.,Johnston, M.E.,Lee, K.U.,Han, In K. Asian Australasian Association of Animal Productio 2000 Animal Bioscience Vol.13 No.11

Prolific females require better nutrition and feeding practice because of larger litter size and the substantial decline in body fat. Life-time pig output will be compromised if body protein and fat are not properly managed. First litter females are especially vulnerable because they can loose ${\geq}15%$ of whole-body protein. Conservation of body protein mass during first lactation minimizes wean to estrus interval and increases second litter size (up to 1.2 pigs). The ability to influence litter-size by amino acid nutrition is a new dimension in our understanding. A P2 fat depth below 12 mm at farrow and below 10 mm at wean compromised wean to estrus interval (>2 d) and next litter size (0.5 to 1.5 pigs) in sows. It is now clear that a 'modest' excess of feed during the first 72 h of pregnancy decreases embryo viability so that the potential for an increased litter size at birth is not realized. The capacity for milk production by prolific young sows is 25% higher than the standard used previously (NRC, 1988). First litter females averaged 9.82 kg milk/d for a 21 d lactation. Second and third litter counterparts averaged 10.35 kg/d. Milk production was 95% of peak by 10 d of lactation and sows were in greatest negative energy and lysine balance during the first 6 d. Nearly 45% of the total loss in body protein occurred within the first 6 d, but this could reduced to 30-35% by using a more aggressive feeding strategy after parturition. There appear to be 2 phases in lactation for lysine need (d 2-12 vs 12-21). Feeding to the higher level alleviates the second litter size decline. The lysine requirement for lactation can be predicted with accuracy, but we are not able to predict the second limiting amino acid. Mammary uptake of valine relative to lysine and recent work with practical diets suggest that the recent NRC (1998) pattern is realistic and that threonine and valine could be co-limiting for corn-soy diets for prolific sows nursing 10-11 pigs. Empirical studies are needed to refine the ideal pattern so that synthetic lysine can be used with more confidence. Milk fat output for the elite sow is extraordinary and poses an unnecessarily high energetic cost. Methods that reduce mammary fat synthesis will benefit the sow and may enhance piglet growth.

청소년 교정환자들의 치은염 및 치아탈회 조절을 위해 사용한 겔형 불화주석(SnF_2 gel)의 장기간 평가

Boyd, Robert L.,전윤식 대한치과교정학회 1995 대한치과교정학회지 Vol.25 No.3

이 논문의 목적은 청소년 교정환자들의 치은염과 치아탈회를 조절하기위해 사용된 수종의 화학요법들에 관해 최근에 보고된 2개의 연구를 재검토하기 위함이다. 첫번째 연구(치은염 연구)는 고정성 교정장치를 장착하고 있는 경우, 기존의 칫솔법에 매일 2회 유효 주석이온이 90%이상 함유된 0.4%의 겔형 불화주석(SnF_2 gel)을 함께 사용하는 경우와 기존의 칫솔법만을 사용하는 것 중 치내침착과 치은염을 조절하는데 있어서 어느 것이 더 효과적인지를 결정하기 위하여 시행 되었다. 두번째 연구(치아탈회 연구)는 교정환자들을 대상으로 1100 ppm의 불소가 함유된 치약만을 사용할 때와 이와 똑 같은 치약과 0.05% 불화나트륨 양치액(NaF rinse)을 병용하여 양치하거나 이 치약과 함께 0.4% 겔형의 불화주석을 사용할 때 치아탈회의 조절효과를 비교하기 위하여 시행 되었다. 치은염 연구에서는 모든 치아를 고정성 장치로 계속 치료를 받고 있는 청소년 교정환자 65명을 연령과 성별에 따라 두 군으로 지정하였다. 마찬가지로 치아탈회 연구에서도 30명을 추가(총 95명)하여 제 3군으로 지정하였다. 제1군(대조군, 35명)은 단지 표준화 불소(1100 ppm 불소) 치약만 사용하였다. 제 2군은 1 군과 같은 치약에 겔형의 0.4% 불화주석이 함유된 치약을(겔형 불화주석군, 표본수=30) 매일 2회씩 18개월 동안 사용하였다. 제 3군은(단지 치아탈회군만으로 이용) 같은 종류의 치약과 0.05% 불화나트륨 양치액을 사용하였다(불화나트륨 양치구, 표본수=30). 치태침착의 임상평가는 Plaque Index로, 치은의 염증은 Gingival Index로, 치관의 착색은 단일맹검(single-blind)으로, 고정성 교정장치를 장착하기 전과 장착한 수 1, 3, 6, 9, 12, 18 개월마다 실시하였다. 치아탈회의 임상평가는 맹출한 모든치아의 순측면에 고정성 교정장치를 장착하기 전과 장치 제거 3개월 후에 단일맹검으로 실시하였다. 치은염 연구에서 겔형 불화주석군(SnF_2 gel group)이 대조군에 비해 교정치료 기간동안 시행한 모든 검사에서 Plaque Index(p<0.01)와 Gingival Index(p<0.001)가 상당히 낮은것으로 나타났다. 겔형 불화주석군에서 한 증례는 미미한 치관착색을, 두 증례는 보통정도의 치관착색을 보였다. 치아탈회 연구에서는 겔형 불화주석군과 불화나트퓸 양치액군이 치료후 치아탈회값에서 치료전 치아탈회값을 뺀 치아탈회값이 대조군에 비해 구강전체및 제1대구치에서 현저하게 낮은 값(p<0.05)을 보였다. 비록 겔형 불화주석군이 불화나트륨 양치액군보다 일관되게 낮은 치아탈회값을 보였을지라도 통계적으로 그 차이는 단지 유의성을 보이는 정도였다. The purpose of this paper is to review two recently reported, long-term studies of several chemical methods to control gingivitis and decalcification in adolescent orthodontic patients. The first study(gingivitis study) was designed to determine whether conventional toothbrushing and twice daily use of a brush-on 0.4 per cent SnF_2 gel containing more than 90 per cent available Sn^2+ would be more effective for controlling plaque accumulation and gingivitis in the presence of orthodontic appliances than conventional toothbrushing alone. The second study(decalcification study) was designed to compare the effectiveness of controlling decalcification in orthondontic patients with either a 1100 ppm F tooth paste used alone, this same toothpaste and a 0.05 percent NaF rinse or this toothpaste and a 0.4 percent SnF_2 gel. In the gingivitis study, sixty-five consecutively treated adolescents who were to receive full-mouth fixed orthodontic appliances were assigned to two groups according to age and sex criteria. In the decalcification study and additional 30 subjects(95 total) were similarly assigned to a third group. The first group(control, n=35) used only toothbrushing with a standard fluoride(1100 ppm F) toothpaste. The second group used toothbrushing with a similar dentifrice supplemented with a 0.4 percent SnF_2 gel(SnF_2 gel group, n=30) used twice daily for the entire 18-month study period. The third group(in the decalcification study only) used a similar toothpaste and 0.05 percent NaF rinse(NaF rinse group, n=30). Clinical assessments of plaque accumulation using the Plaque Index, gingival inflammation using the Gingival Index, and coronal staining were completed single-blinded before appliances were placed and 1, 3, 6, 9, 12 and 18 months after appliances were placed. Decalcification was assessed single blind on all labial surfaces of all erupted teeth before appliances were placed and 3 months after appliances were removed. The results of the gingivitis study indicated that the SnF_2 gel gorup had significantly lower scores for the Plaque Index(p<0.01) and Gingival Index(p<0.001) at all examinations during orthodontic treatment than did the control group. In the SnF_2 gel group, one subject developed mild coronal staining and two subjects developed moderate staining. In the decalcification study, when pre-treatment levels of decalcification were subtracted from post-treatment values, significantly lower decalcification scores(p<0.05) were found for both whole mouth and first molars in the NaF rinse and gel groups as compared with the control group(toothpaste alone). Although the gel group consistently had less decalcification than the rinse group, this difference only approached statistical significance.

Issues of Collective Management in the Pacific

Boyd, Gavin Center for International Studies, Inha University 1986 Pacific Focus Vol.1 No.2

A PACIFIC REGIONAL ECONOMIC ORDER

Boyd,Gavin The Institute for Far Eastern Studies Kyungnam Uni 1983 ASIAN PERSPECTIVE Vol.7 No.1

ARGUMENT ANALYSIS AND CRITICAL THINKING

Robert Boyd 대한사고개발학회 1993 The International Journal of Creativity & Problem Vol.3 No.2

Holomorphic functions and the BB-property on product spaces

Christopher Boyd 대한수학회 2004 대한수학회지 Vol.41 No.1

In [25] Taskinen shows that if {En}n and {Fn}n are two sequences of Fr´echet spaces such that (Em, Fn) has the BBproperty for all m and n then m Em,n Fn also has the BBproperty. Here we investigate when this result extends to (i) arbitrary products of Fr´echet spaces, (ii) countable products of DFN spaces, (iii) countable direct sums of Fr´echet nuclear spaces. We also look at topologies properties of (H(U), τ) for U balanced open in a product of Fr´echet spaces and τ = τo, τω or τδ.