Study on design parameters of leaning-type arch bridges

Ying Li,Ru-Cheng Xiao,Bin Sun 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.2

Leaning-type arch bridge is a new spatial structural system composed of two vertical arches and two leaning arches. So far there has been no contrast analysis of leaning type arch bridge with different systems. This paper focus on a parametric study of leaning type arch bridge with different systems to find the influential rules on structural forces and stability and to provide some reference for practical designs. The parametric analysis is conducted with different rise-to-span ratios and bending rigidities of arch ribs by comparing internal forces. The internal forces decline obviously with the increase of the rise-to-span ratio. The bending moments at the centers of the main arches and the leaning arches are sensitive to the bending rigidities of arch ribs. Parametric studies are also carried out with different structural systems and leaning angles of the leaning arch by comparing the static stability. The lateral stiffness of leaning-type arch bridge is less than the in-plan stiffness. Compared with the leaning-type arch bridge without thrust, the leaning-type arch bridge with thrust has a lower stability safety coefficient. The stability safety coefficient rises gradually with the increase of inclining angle of the leaning arch. This study shows that the rise-to-span ratio, bending rigidities of arch ribs, structural system and leaning angles of the leaning arch are all critical design parameters. Therefore, these parameters in unreasonable range should be avoided.

Lean Six Sigma 기법을 이용한 생산시스템 개선 및 확장 모델 연구

서장훈 동의대학교 경제경영전략연구소 2009 經濟經營硏究 Vol.4 No.2

Lean Six Sigma(LSS) is a business improvement methodology which combines (as the name implies) tools from both Lean Manufacturing and Six Sigma. Lean manufacturing focuses on speed and traditional Six Sigma focuses on quality. By combining the two, the result is better quality faster. Both the Lean and the Six Sigma methodologies have proven over the last twenty years that it is possible to achieve dramatic improvements in cost, quality, and time by focusing on process performance. Therefore, many firms are looking for an approach that allows to combines both methodologies into an integrated system or improvement roadmap. However, the differences between the Six Sigma and Lean are profound. Using Lean Six Sigma for strategic advantage in Business flow. The ROI of Lean Six Sigma for services Getting faster to get better(why you need both Lean and Six Sigma) Improving services. As a Result, Lean Six Sigma System derives the long-term success for the powerful management system. This paper shows that the execution of Lean 6sigma method can be successful only if the management officers' interest and support are back up. And we suggest a guideline that continuous improvement factors and performance Tool are the most necessary factors for the successful cooperation management using LSS

Lean이 기업성과에 미치는 영향 : 종업원의 노동유연성의 매개효과 중심으로

박정우 한국경영컨설팅학회 2014 경영컨설팅연구 Vol.14 No.3

본 연구는 기업의 혁신적 경영기법인 Lean을 도입한 기업이 어떠한 인프라를 구축하였으며, 그 성과는 어떻게 나타나는지 분석해 보았다. 그 과정에서 Lean의 현장을 담당하고 있는 종업원의 노동유연성이 어떠한 매개효과를 가지는지 실증적으로 분석해 보았다. 연구를 진행하기 위해 Lean을 도입한 기업의 129명으로부터 자료를 수집하여 실증 분석을 실시하였다. 연구 결과 Lean 인프라는 Lean, 기업성과에 유의한 영향을 미치고 있고, Lean 제조 또한 기업성과에 유의한 영향을 미치고 있었으며, 그 사이에서 종업원의 노동유연성은 부분적으로 매개효과가 있는 것으로 나타났다. 이러한 실증분석 결과는 Lean을 실행하기 위해 Lean 인프라의 구축과 더불어 Lean을 실천하는 종업원의 개인적인 능력도 중요함을 시사하고 있으며 분석결과를 토대로 연구의 의의와 한계점 및 향후 연구 제언을 실시하였다.

재고최소화와 에너지효율성 간의 관계에 대한 실증분석: 국내 철강기업을 중심으로

김길환 공주대학교 KNU 기업경영연구소 2022 기업경영리뷰 Vol.13 No.3

Energy efficiency is critical issue for steel companies because they consume a lot of energy in the produc- tion process. Also, inventory management is one of the paramount management activities for steel companies because they mainly produce intermediate goods. This study aims to investigate the relationship between inven- tory management, which is the important management activity to steel companies, and energy efficiency, which is critical due to the nature of their production process. To achieve this goal, we define energy efficiency with distance function and estimate it using stochastic frontier analysis. Morovere, given that lean inventory manage- ment has been widely applied among most companies, we adopt the concept of inventory leanness to evaluate the level of inventory management within the steel company and use emprical leanness indicator to estimate inventory leanness. Also, we consider energy efficiency as a dependent variable and empirical leanness indicator as a independent variable to exmaine the relationship between energy efficiency and inventory leanness, and we analyze the impacts of company size and industry dynamism on energy efficiency. The main results of this study are as follows. First, the average energy efficiency is around 0.901, which is lower than the optima energy efficiency. Second, both company size and industry dynamism have the negative impacts on energy efficiency. Based on these results, we provide the managerial implication as follows. First, in order to improve energy ef- ficiency, it is necessary for the managers of steel company to actively introduce the lean approach for the inven- tory management. Second, it is required for the mangers of large steel company to examine whether energy is efficiently used in production process. Meanwhile, this study contributes to the related literature by analyzing the relationship between inventory leanness and energy efficiency―not addressed in previous studies―and then revealing the effectiveness of lean inventory management in terms of energy efficiency 에너지를 많이 소비하는 생산시스템의 특성상 철강기업의 에너지효율은 중요한 이슈이다. 또한 철강기업은 중 간재를 주로 생산하므로 재고관리가 핵심 관리 활동 중의 하나이다. 본 연구는 철강기업의 ‘핵심 관리 활동인 재 고관리’와 ‘생산시스템의 특성상 매우 중요한 에너지효율’의 관계를 검토해 보고자 하였다. 이를 위해 거리함수 (Distance Function)에 근거하여 에너지효율성(Energy Efficiency)을 정의한 후 확률변경분석(Stochastic Frontier Analysis)을 통해 에너지효율성을 추정하였다. 그리고 린방식(Lean Practice)의 재고관리 접근이 기업들 사이에 광 범위하게 적용되어 왔다는 점을 감안하여 철강기업의 재고관리 수준을 평가하기 위한 개념으로 재고최소화(In- ventory Leanness)를 채택하였고, 실증최소화지표(Empirical Leanness Indicator)로써 이를 추정하였다. 또한 에너 지효율성과 재고최소화의 관계를 검토하기 위해 에너지효율성을 종속변수로, 실증최소화지표를 독립변수로 하 여 분석을 진행하였다. 추가로 에너지효율성에 미치는 기업 규모와 산업역동성(Industry Dynamism)의 효과도 검 토하였다. 주요 분석 결과는 다음과 같다. 첫째, 분석대상 철강기업의 평균 에너지효율성은 0.901로 최적의 에너 지효율성 수준보다 낮은 수준에서 실제 에너지효율성이 결정되고 있다. 둘째, 재고최소화는 에너지효율성에 양의 영향을 주고 있다. 셋째, 기업 규모 및 산업역동성은 에너지효율성에 음의 영향을 주고 있다. 이와 같은 주요 결과 를 토대로 다음과 같은 시사점을 제시하였다. 첫째, 에너지효율성 개선을 위해 철강기업의 관련 실무자는 린방식 의 재고관리를 적극 도입할 필요가 있다. 둘째, 규모가 큰 철강기업의 관련 실무자는 에너지 사용이 효율적으로 이루어지고 있는지를 검토해 볼 필요가 있다. 한편, 본 연구는 기존 연구에서 고려되지 않았던 재고최소화와 에너 지효율성 간의 관계를 분석하여, 에너지효율 개선 측면에서 작동하는 린방식 재고관리의 효과성을 밝혀냈다는 점 에서 관련 연구에 기여하고 있다.

LEAN-NPD적용에 따른 구조방정식모델 실증분석

김계수 ( Gye Soo Kim ),정성택 ( Seong Taek Jeong ) 한국품질경영학회 2013 품질경영학회지 Vol.41 No.3

Purpose: This study is about Lean-NPD (New Product Development), Lean-NPD is Pulip Line`s New Product Development type. This study introduced Lean-NPD Definition, Case Study, and Research Model of Lean-NPD, Empirical results of this survey will be provide suggestions to workers. Methods: Researcher developed research model about Lean-NPD activities. And researched Lean-NPD, This study analyzed model fitness and path significant with SEM(Structural Equation Model). Results: Fitness of the research model was satisfactory level. Leadership capabilities and production oper-ations were significantly influence marketing capabilities(t>±1.96). Organizational culture significantly affected marketing capabilities(t>±1.96). R&D capabilities and marketing competencies had significant influence on business performance(t>±1.96). Marketing capabilities had significant influence on quantitative management performance(t>±1.96). Outstanding leadership appear to directly affect Qualitative Perforrnance(t>±1.96). Conclusion: Under the excellent leadership and management environment definite organic Lean-NPD organizational culture significantly affects the operation can be seen. Lean-NPD of operational activities to provide value to customers, customer-oriented marketing activities can be seen that more important than anything. Lean NPD based on customer needs is key factor of growth.

An assessment of the ultra-lean combustion direct-injection LPG (liquefied petroleum gas) engine for passenger-car applications under the FTP-75 mode

Kim, J.,Kim, K.,Oh, S. Elsevier Scientific Pub. Co 2016 Fuel processing technology Vol.154 No.-

Fuel economy and emissions characteristics of the lean-burn combustion strategy were assessed in a direct-injection liquefied petroleum gas engine under urban driving conditions. This study investigated: (1) engine experiments under steady-state conditions that frequently occur during city driving and (2) zero-dimensional drive cycle simulation under the FTP-75 mode. From the engine experiments, two sets of operation maps were constructed for the lean and conventional combustion modes. The lean combustion set consisted of the lean operation between 20 and 80Nm and the stoichiometric operation for the rest of the operating envelope. The selected lean operation range was found to be the largest possible to operate under the lean condition. The entire conventional combustion set was taken at the stoichiometric condition for comparison with the lean combustion set. Then, the steady-state performance maps of the fuel consumption, emissions, and exhaust temperature of the two combustion sets were used in a vehicle model of the cycle simulation. The drive cycle simulation results showed that the fuel economy of the lean combustion set was 10.65km/l, which is lower than that of the conventional combustion set by 6.3%. Carbon dioxide emission was 146.25g/km, down by 8g/km from the conventional combustion set. The time-resolved emissions of the particle mass and particle number of the lean combustion set were 0.005g/km and 3.2x10<SUP>11</SUP>#/km, respectively. The particle emissions of the lean combustion set were higher than those of the conventional combustion set, but considered as acceptable levels based on the upcoming emission standards.

A comparative study of lean burn and exhaust gas recirculation in an HCNG-fueled heavy-duty engine

Park, Cheolwoong,Lee, Sunyoup,Kim, Changgi,Choi, Young Elsevier 2017 International journal of hydrogen energy Vol.42 No.41

<P><B>Abstract</B></P> <P>Two dilution strategies, exhaust gas recirculation (EGR) with a stoichiometric mixture and excess air with a lean mixture, were investigated for an 11 L, 6-cylinder H<SUB>2</SUB>-blended compressed natural gas (HCNG) engine. The engine was operated at 1260 rpm and 50% of maximum engine load (575 Nm) at maximum brake torque for each strategy. To evaluate the EGR approach, the stoichiometric combustion mode was varied, and to evaluate the lean combustion mode, the excess air ratio was varied. The maximum EGR rate and lean flammability limit were constrained by the combustion stability. The dilution rate was employed to compare the dilution effect on engine performance and emission levels under identical levels of the dilution for both combustion modes. The thermal efficiencies under stoichiometric combustion with EGR were lower than those under lean combustion, owing to a higher pumping loss and a lower combustion speed. The total hydrocarbon emissions under the lean combustion mode were lower than those under the stoichiometric combustion mode only when the combustion speed was relatively slow, due to the higher mixing rate caused by the active combustion. As the dilution rate was increased in the lean combustion mode, the rate of decrease in NO<SUB>x</SUB> emissions slowed compared to the stoichiometric combustion mode. The lowest level of engine-out NO<SUB>x</SUB> emissions was observed under lean combustion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The maximum dilution rates of an HCNG engine are 27.3% for EGR and 48.6% for lean-burn. </LI> <LI> The efficiency with EGR is lower owing to pumping loss and combustion temperature. </LI> <LI> THC emissions with lean-burn are lower under a low combustion speed because of mixing rate. </LI> <LI> The lowest level of engine-out NOx is observed with lean-burn. </LI> </UL> </P>

린 스타트업 방법론의 적용: 한국 ‘카닥’ 사례를 중심으로

나희경,이희우 한국벤처창업학회 2016 벤처창업연구 Vol.11 No.5

The Lean Startup, a methodology for minimizing failure rate of startups, has been receiving attention since its publication in 2011. Although it has been receiving enormous attention as an effective methodology of startups' growth and the emergence of unicorn companies, it is undeniable that the theoretical research and cases on this topic have not been fully accumulated in Korea. Progress of management theory has been made when combining the theory and case studies. In this paper, we thus excavated the 'Cardoc' case, which has applied the lean startup concept to the entire process of service and customer development from the inception of its product design. The following are the findings of the case. First, for the successful application of lean startup, it is essential that all team members to understand the lean startup concept and are willing to apply it thoroughly to the business management. Second, the prompt launching of MVP (Minimum Viable Product) is more important than table discussion. Third, it is crucial to select the appropriate key metrics and analytic tools for effective learning. Fourth, startup must scale up promptly as soon as it verifies the product-market fit through the BML (Build-Measure-Learn) iteration cycle. Fifth, all new business expansion should be lean. Cardoc is currently testing new MVPs in order to move onto the next scale-up process with huge investments in newly added segments. This study is meaningful in that it elaborates the representative case of a Korean startup that has applied the lean startup strategy under the circumstance of insufficient discussion of Korean startup cases in comparison with growing attention both in concept development and case accumulation abroad. We hope that this paper can be a stepping stone for future relevant research on the implementation of lean startup methodology in Korea. 창업 성공률을 제고하고 실패 가능성을 낮추는 경영전략으로써‘린 스타트업’은 2011년 에릭 리스의 책 출간 이후 줄곧 주목을 받아왔다. 전 세계적인 유니콘 스타트업의 등장과 창업 초기기업에 보다 효과적인 성장 방법론으로써의 린 스타트업에 대한 관심 고조에도 불구하고 한국에서는 체계적인 관련 이론연구와 사례 축적이 미진한 상황이다. 경영학의 진정한 발전은 이론과 그것을 기반으로 한 다양한 사례와의 접목이 이루어질 때 가능하다. 이에 본 논문에서는 서비스 개발 초기부터 린 스타트업의 개념이 적용되었고 서비스와 고객 개발의 전 과정에서 린 개념이 적극적으로 도입된 한국기업 ‘카닥’의 사례를 발굴하고 고찰하였다. 본 연구를 통해 알게 된 사실은 다음과 같다. 첫째, 린 스타트업 적용을 위해서는 우선 린 스타트업을 적용하려는 경영진, 팀원 들이 모두 그 개념을 깊이 이해하고 적용의 필요성에 공감해야 한다. 둘째, 수많은 논의보다 빠른 MVP(최소요건제품)의 출시가 우선이다. 셋째, 효과적인 학습을 하기 위해서는 적합한 분석툴과 핵심지표(Key Metrics) 선정이 무엇보다 중요하다. 넷째, 만들기-측정-학습(Build-Measure-Learn)의 사이클을 통해 지속적으로 측정하고 배워 제품/시장 적합성(Product-Market Fit)이 검증되었다면 과감히 규모를 확장해야 한다. 다섯째, 신규사업 진출도 철저히 린 하게 해야 한다. 카닥은 현재 신규사업으로 확장을 꾀하는 중으로 이 역시 린 스타트업 방법론을 철저히 적용하여 시범서비스(MVP)로 그 가능성을 타진해 본 후 투자를 본격화 한다. 본 연구는 린 스타트업에 관련한 기존 개념의 논의와 더불어 그 적용사례가 축적되고 있는 외국과 비교해, 한국 기업의 사례연구가 절대적으로 부족한 현 상황에서 한국의 대표적인 린 스타트업 활용 사례를 고찰하였다는 점에서 의의가 있다고 할 수 있다. 본 연구가 린 스타트업 방법론의 국내 적용과 향후 관련 연구에 하나의 디딤돌이 되기를 바란다.

린 생산효율성에 따른 재고자산의 보유수준이 경영성과에 미치는 영향

성현정 ( Hyunjung Sung ),김석수 ( Seogsoo Kim ) 한국로지스틱스학회 2017 로지스틱스연구 Vol.25 No.2

지난 30년 간 많은 기업들이 효율적인 생산운영방식의 하나로 린 생산(Lean Production)을 달성하기 위해 지속적으로 노력하였으나 실제 이러한 린 생산방식이 기업 경영성과를 향상시키는지에 대해서는 연구자 간 합의가 부족한 실정이었다. 따라서 본 연구는 재고를 하나의 낭비(waste)로 인식하는 린 생산의 관점을 바탕으로 기업은 최소한의 재고를 유지하는 관리방식을 활용할 것으로 예상하여 린 생산 효율성에 따른 재고자산의 보유수준과 기업 경영성과 간의 관계를 파악하고자 하였다. 이에 2000년부터 2013년까지 한국거래소에 상장된 결산법인 중 제조업에 해당하는 총 421개의 기업을 대상으로 재고자산의 보유수준과 경영성과 간의 관계를 선형모형과 비선형모형으로 설정하여 고정효과모형으로 분석하였고 두 모형 간 설명력을 비교하는 방식을 활용하였다. 그 결과 전체 제조업을 대상으로 한 분석 결과에서 비선형모형이 적합한 것으로 나타났으며 이때 역 U자의 관계를 형성하는 것으로 드러났다. 이는 재고보유로 인한 비용과 위험의 상충관계를 고려하였을 때 최적의 재고보유 수준을 유지하는 것이 기업의 경영성과에 긍정적인 영향을 미치는 것으로 해석할 수 있다. 두 번째로는 전체 제조업을 주요 12개의 산업별로 분류하여 위와 동일한 방식으로 분석을 실시하였고 그 결과 12개의 산업 중 7개의 산업은 재고자산의 보유수준과 경영성과 간의 관계를 선형모형으로 설명하는 것이 적합했으며 이때 둘 사이에는 부(-)의 관계를 띄는 것으로 나타났다. 반면 4개의 산업은 비 선형모형으로 설명하는 편이 더 적절하였는데 이는 전체 제조업을 대상으로 한 분석 결과와 동일하게 재고자산의 보유수준과 기업의 경영성과 간의 역 U자형의 관계를 형성하는 것으로 나타났다. 이러한 산업별 차이는 산업의 구조적 특성으로 인한 기업의 운영방식의 차별화됨으로써 적정재고량 및 재고관리방식이 상이할 것으로 예상된다. While many firms have adopted lean production increasingly, there is a little evidence that lean production leads to improved firm performance. Based on the lean production philosophy, lean inventory management became synonymous with the best inventory management (Zipkim, 1991; Chen et al., 2005). Thus, this study analyzes the relation between the inventory level and the financial performance of Korean manufacturing industries from 2000 to 2013. The analysis results are as follows. First, there is an inverted U-shaped relationship between the inventory level and firm`s financial performance. This result suggests that there is an optimal degree of inventory leanness. Furthermore, the benefits of lean inventory strategies are exhausted, and the incremental effect of inventory leanness on firm performance is decreased from the certain point. Second, the relationship between inventory level and firm performance is quite different according to the industry type. Only 4 industries of the 12 industries can be applied to an inverted U-shaped relationship, but rather the reminders have a negative relationships between the inventory level and financial performance. In spite of that, this study can provide the empirical support for the pragmatic JIT view which asserts that leaner is not always better.

Economic evaluation of NGL recovery process schemes for lean feed compositions

Jin, Chunhe,Lim, Youngsub Elsevier 2018 Chemical engineering research & design Vol.129 No.-

<P><B>Abstract</B></P> <P>The economic analysis of lean feed conditions for natural gas liquids (NGL) recovery is required to meet recent increases in the demand for lean gas reservoirs. This paper compares the economic performance of various NGL recovery schemes with consideration of the LNG HHV specification under various lean feed compositions. The ISS and IPSI schemes are typical processes in NGL recovery, especially in the normal and rich fields, whereas HHC separator and scrub column schemes have advantages for lean feeds. All the schemes were built by HYSYS simulation software and optimized using a genetic algorithm. The profitability analysis indicates that the gross profit and payout time give a similar trend compared to the previous studies. However, the results give different outcomes when considering total annualized cost (TAC), especially in terms of lean feed condition. The results show that scrub column scheme shows the best economic performance compared to other schemes under lean feed compositions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Comparing representative NGL recovery processes for lean feed compositions. </LI> <LI> The higher heating value and C<SUB>5+</SUB> contents are considered for LNG specification. </LI> <LI> Scrub column scheme shows optimum performance when the feed is considerably lean. </LI> </UL> </P>