Fixture layout optimization for multi point respot welding of sheet metals

Zeshan Ahmad,Tipu Sultan,Muhammad Asad,Matteo Zoppi,Rezia Molfino 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

The high quality of welding in the automotive industry is achieved by proper positioning of the fixture elements. A new method, N-3-2-1 (N ≥ 1), is proposed for fixture layout optimization of sheet metals. The flexible nature of the sheet metals requires N+3 fixture elements to constrain it normal to the surface (primary plane), but 2-1 fixture elements for other two directions (secondary and tertiary). The objective function is to achieve high stiffness of the workpiece and is calculated in terms of strain energy. Finite element analysis (FEA) was combined with genetic algorithm. A method was also proposed to find the optimum fixturing position of the workpiece in multipoint respot welding operation. Two different kinds of case studies were solved and the performance of the proposed method was also tested in the industrial scenario by fixturing the workpiece and completing the respot welding operation with satisfactory results.

The Focused Electrode Ring for Electrohydrodynamic Jet and Printing on Insulated Substrate

Zeshan Abbas,Dazhi Wang,Liangkun Lu,Zhaoliang Du,Xiangyu Zhao,Kuipeng Zhao,Meng Si,Penghe Yin,Xi Zhang,Yan Cui,Junsheng Liang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.5

Drop-on-demand electrohydrodynamic jet (DoD E-Jet) printing is considered a well-known type of fabrication method contemporary since it can be used to print high-resolution microstructures (< 1 μm) on various insulating substrates. This paper presents a numerical study of DoD E-Jet printing using a novel combination of needle and focused electrode ring to print stable and consistent microdroplets on a Polyethylene terephthalate substrate. Primarily, a phase field method was used to generate a stable cone-jet morphology that can allow the production of high-resolution micron/nano structures on PET substrates. The numerical simulation of cone-jet morphology was performed by COMSOL multiphysics software. Further, the impact of key parameters such as flow rate and dc positive pulse voltage was studied on cone-jet morphology through numerical simulation. Subsequently, optimized operating parameters i.e., f = 5.3 . 10 –15 m 3 s −1 , V n = 1.9 kV and V r = 0.7 kV were achieved by performing a series of numerical experiments. Then, optimized parameters by simulation were directly used to print arrays of stable droplets on PET substrate using the focused electrode ring in different locations by regulating distance 0.2 mm to 1.3 mm between needles to focused electrode ring. The minimum size of stable microdrop was measured 3 μm on PET substrate (thickness = 0.2 mm) using a 50 μm size quartz capillary maintaining a distance of 0.2 mm between combined needle and focused electrode ring. The experimental results proved that the simulation model is useful for printing different microstructures on insulating substrates and creating a promising production path for micro-electro mechanical system and nano-electro mechanical system (MEMS and NEMS).

Synthesis of Needle-Like Aragonite Crystals in the Presence of Magnesium Chloride and Their Application in Papermaking

Hu, Zeshan,Shao, Minghao,Li, Huayang,Cai, Qiang,Zhong, Chenghua,Xianming, Zhang,Deng, Yulin The Korean Society for Composite Materials 2009 Advanced composite materials Vol.18 No.4

PCC (precipitated calcium carbonate) and ground calcium carbonate have been widely used in alkaline papermaking. Unfortunately, although increasing filler level in papers can improve the paper properties such as brightness, opacity, stiffness gloss, smoothness, porosity, and printability, as well as decrease cost, some strength of the paper is negatively affected. In this research, needle-like aragonite was synthesized using $Ca(OH)_2$ and $CO_2$ as reactants in the presence of $MgCl_2$ and characterized with scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The physical and optical properties of the paper handsheets containing these needle-like aragonite fillers were evaluated. Results indicated that tensile strength, Z-direction tensile strength and folding endurance of the paper were improved by the needle-like aragonite crystals compared to the paper using commercial PCC (precipitated calcium carbonate) as filler. The stiffness of the paper handsheet on the machine direction was increased, but no evident difference in the cross direction was found. The improvement of paper strength mainly resulted from the twining effect between the aragonite whiskers and paper fibers. The optical properties of the paper were slightly decreased with the use of the needle-like aragonites compared to commercial PCC. These results suggest that paper cost can be decreased by increasing the content of needle-like aragonite filler while paper strength will not be decreased compared to PCC filler.

CGE모형을 이용한 2015년 파리기후변화협정의 국가별 이산화탄소 배출감소 이행안 시행의 경제적 영향분석

( Muhammad Zeshan ),고종환 ( Jong-hwan Ko ) 한국국제통상학회 2016 국제통상연구 Vol.21 No.4

논문은 2가지 연구목적을 가지고 있다. 하나는 2015년 파리기후변화회의에서 합의한 국가별 이산화탄소 배출감소안(INDCs)을 이행하는 경우, 세계경제와 관련국가 경제에 미치는 영향을 분석하는 것이며, 다른 하나는 이산화탄소 배출감소안(INDCs)을 제시하지 않은 국가들이 어느 정도 이산화탄소 배출을 줄이는 것이 바람직할 것인가를 도출하는 것이다. 본 연구에서는 GTAP-E model과 2016년 2월 발표된 GTAP version 9 satellite database를 활용하였다. 연구 목적상 GTAP version 9 satellite database에 포함되어있는 140개 국가와 57개 산업을 각각 14개 국가와 10개 산업으로 통합하여 사용하였다. 2가지 시나리오를 상정하였다. 하나는 이산화탄소 거래제와 같은 제도를 도입하지 않고 이산화탄소 배출을 줄이는 경우이며(시나리오1), 다른 하나는 이산화탄소 거래제와 같은 제도를 활용하여 이산화탄소 배출을 줄이는 경우(시나리오2)이다. 시뮬레이션 결과를 보면, 이산화탄소거래제와 같은 제도를 활용함으로써 이산화탄소 한계배출비용을 크게 줄일 수 있는 것으로 분석되었다. 한국의 경우, 1톤당 이산화탄소 한계배출비용이 $134.7에서 $59.2로 줄어들며, 중국의 경우 $144.8에서 $59.7로 줄어들고, 일본의 경우 $127.8에서 $59.2로 줄어들며, EU27의 겨우 $222.8에서 $59.3 로 줄어들고, RoA1.의 경우 $121.7에서 $59.7로 줄어드는 것으로 분석되었다. 이산화탄소 거래제와 같은 제도를 활용함으로써 전세계적으로 약 4,000억$의 비용을 줄일 수 있을 것으로 분석되었다. This paper aims at two objectives. First, it addresses the CO₂ emission reduction targets committed in the Paris Climate Conference 2015 - also known as the INDCs - and measures their global economic implications. Second, it finds out the possible INDC targets for the regions that have not committed their INDC targets yet. It uses the GTAP-E model and the GTAP version 9 satellite database released in February 2016. It contains 140 regions and 57 sectors for each region. However, for analytical convenience, 140 regions and 57 sectors have been aggregated into 14 regions and 10 sectors, respectively. Two scenarios are run in this study. In scenario 1, it is assumed that countries are bound to meet their INDC targets without trade in CO₂ emissions. In scenario 2, it is assumed that countries are allowed to use flexibility mechanisms such as emission trading (ET) and joint implementation (JI). The simulation results show that global trade in CO₂ emissions reduces the marginal abatement costs per ton of CO₂ emissions from US$134.7 to $59.2 for Korea, $144.8 to $59.7 for China, $127.8 to $59.2 for Japan, $222.8 to $59.3 for EU27 and $121.7 to $59.7 for RoA1. Emission trading through the flexible mechanisms save globally around $400 billion.

Climate Change and Agriculture: A Computable General Equilibrium Approach

Muhammad Zeshan,Jong-Hwan Ko 한국무역연구원 2017 무역연구 Vol.13 No.6

This paper quantifies the impact of climate change on agriculture in East Asian and South Asian countries using a CGE based energy model and the latest GTAP satellite energy database version 9. The rising temperature causes an adverse supply shock reducing the productivity of agricultural commodities. Lower productivity reduces crop production while increasing their prices. India and Pakistan are predicted to be the main net exporters of rice while China, Japan and Korea are the main net importers of wheat, vegetables and fruits, oil seeds, sugarcane and other agricultural products after climate change. Finally, both the welfare level and GDP decrease in most of the East Asian and South Asian countries after climate change and China is expected to bear the highest GDP losses. Although climate change might increase the number of poor in East Asia and South Asia, however it provides many options for green businesses.

Synthesis of Needle-like Aragonite from Limestone without Calcinations in the Presence of Magnesium Sulfate

Hu, Zeshan,Shao, Minghao,Cai, Qiang,Jiao, Zhaojie,Zhong, Chenhua,Deng, Yulin The Korean Society for Composite Materials 2009 Advanced composite materials Vol.18 No.2

Much attention has been paid to the processing of inorganic whisker, especially calcium carbonate whisker, which can be used as reinforcement materials of polymer composite due to its low price. Unfortunately, the present synthesis technique of calcium carbonate whisker starts from calcinations of limestone, which involves high energy consumption and furthermore is a highly environment polluting reaction. In this report, needle-like aragonite was synthesized with a reversible solution reaction from limestone without calcination. Optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to characterize the morphology and crystal structure of intermediates as well as that of the product, aragonite. GCC (grinding calcium carbonate) powder was dissolved in an aqueous solution of magnesium sulfate with reflux and air flush. EDTA titration was used to evaluate reaction rate of the dissolution. A kinetics equation of the dissolution reaction was constructed, which displayed second-order kinetics with respect to the concentration of magnesium sulfate. A rate constant of $0.0015\;l^{-3}{\cdot}mol^{-1}{\cdot}h^{-1}$ was obtained. The dissolution reaction gave fiber-like magnesium hydroxide sulfate and gypsum crystal. Then needle-like aragonite with a length of $9.13\;{\pm}\;1.02\;{\mu}m$ and an aspect ratio of $5.64\;{\pm}\;1.37$ was synthesized from the dissolution product with $CO_2$ bubbling at $70^{\circ}C$.

Implementation of VANET-based Warning Generation System using Cellular Networks, GPS, and Passive RFID Tags

Farhan Aadil,Zeshan Iqbal,Adeel Akram 한국산학기술학회 2012 SmartCR Vol.2 No.6

Vehicular communication systems are a key part of an intelligent transportation system, while vehicle safety communication is a major target of vehicular communication. Other features that augment vehicular ad hoc networks are enhanced driving experience, including but not limited to, active navigation and weather information, real-time traffic information and a plethora of other autonomous and automated systems. However, our focus will be warning generation systems, which can help reduce fatalities if deployed in an efficient and fail-safe manner on motorways and highways. This paper describes a collective information system for collection and delivery of traffic information aimed at supporting fast, efficient and secure travel of people and transport of goods. Based on that information, authorities are able to assess vehicles’ sudden motion and movement changes and can generate warning/alert messages (for emergency/police vehicles) for post-accident scenarios. In this paper, the use of a radio frequency identification (RFID) system for vehicular communication has been proposed and an extended RFID system and infrastructure for vehicle safety communication through emergency phone towers (EPTs) and cell phones is suggested. In order to communicate, vehicles may be equipped with a cellular phone, RFID, and/or a global positioning system (GPS), whereas RFID readers may be mounted on EPTs, which are already installed on motorways. It also provides a demonstration on flow of information within the system; the simulation results are also included.

Microsecond molecular dynamics simulations revealed the inhibitory potency of amiloride analogs against SARS-CoV-2 E viroporin

Jaber, Abdullah All,Chowdhury, Zeshan Mahmud,Bhattacharjee, Arittra,Mourin, Muntahi,Keya, Chaman Ara,Bhuyan, Zaied Ahmed Korea Genome Organization 2021 Genomics & informatics Vol.19 No.4

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) encodes small envelope protein (E) that plays a major role in viral assembly, release, pathogenesis, and host inflammation. Previous studies demonstrated that pyrazine ring containing amiloride analogs inhibit this protein in different types of coronavirus including SARS-CoV-1 small envelope protein E (SARS-CoV-1 E). SARS-CoV-1 E has 93.42% sequence identity with SARS-CoV-2 E and shared a conserved domain NS3/small envelope protein (NS3_envE). Amiloride analog hexamethylene amiloride (HMA) can inhibit SARS-CoV-1 E. Therefore, we performed molecular docking and dynamics simulations to explore whether amiloride analogs are effective in inhibiting SARS-CoV-2 E. To do so, SARS-CoV-1 E and SARS-CoV-2 E proteins were taken as receptors while HMA and 3-amino-5-(azepan-1-yl)-N-(diaminomethylidene)-6-pyrimidin-5-ylpyrazine-2-carboxamide (3A5NP2C) were selected as ligands. Molecular docking simulation showed higher binding affinity scores of HMA and 3A5NP2C for SARS-CoV-2 E than SARS-CoV-1 E. Moreover, HMA and 3A5NP2C engaged more amino acids in SARS-CoV-2 E. Molecular dynamics simulation for 1 ㎲ (1,000 ns) revealed that these ligands could alter the native structure of the proteins and their flexibility. Our study suggests that suitable amiloride analogs might yield a prospective drug against coronavirus disease 2019.

등가하중을 이용한 비선형 정적 응답 위상최적설계의 기초연구

이현아(Hyun-Ah Lee),Ahmad Zeshan,박경진(Gyung-Jin Park) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.12

실제 대부분의 공학 문제들은 크고 작은 비선형성을 내포한다. 구조물의 최적설계 과정에서는 다수의 구조물 사이에 발생하는 접촉이나 비선형 물성치를 가지는 재료, 또는 대변형을 고려해야만 한다. 그러나 민감도 계산이 고가이기 때문에 비선형성을 최적화에 고려하는 것은 매우 어렵다. 따라서 비선형 정적 반응 위상최적설계를 위하여 등가하중법을 사용한다. 등가하중이란 비선형 해석에서 유발되는 반응장과 동일한 반응장을 유발하는 선형 정적하중이다. 등가하중법은 치수/형상최적설계를 위하여 연구되어 왔다. 위상최적설계는 치수/형상최적설계에 비하여 설계변수가 많기 때문에 기존의 등가하중법을 그대로 적용할 수 없기 때문에 위상최적설계를 위하여 등가하중법을 확장하고 수정한다. 간단한 예제를 통하여 등가하중법을 이용한 위상최적설계 결과가 수치적으로 도출한 결과와 유사함을 보이고 실제 공학 예제의 위상최적설계를 통하여 기존의 선형 정적 위상최적설계와 결과를 비교한다. Most components in the real world show nonlinear response. The nonlinearity may arise because of contact between the parts, nonlinear material, or large deformation of the components. Structural optimization considering nonlinearities is fairly expensive because sensitivity information is difficult to calculate. To overcome this difficulty, the equivalent load method was proposed for nonlinear response optimization. This method was originally developed for size and shape optimization. In this study, the equivalent load method is modified to perform topology optimization considering all kinds of nonlinearities. Equivalent load is defined as the load for linear analysis that generates the same response field as that for nonlinear analysis. A simple example demonstrates that results of the topology optimization using equivalent load are very similar to the numerical results. Nonlinear response topology optimization is performed with a practical example and the results are compared with those of conventional linear response topology optimization.

RaptorQ-Based Efficient Multimedia Transmission Over Cooperative Cellular Cognitive Radio Networks

Ali, Amjad,Kwak, Kyung Sup,Tran, Nguyen H.,Han, Zhu,Niyato, Dusit,Zeshan, Farukh,Gul, M. Talha,Suh, Doug Young IEEE 2018 IEEE Transactions on Vehicular Technology VT Vol.67 No.8

<P>Accommodating the fast-growing multimedia traffic demands at low cost is critical to ensure the future competitiveness of cellular networks. Cognitive radio (CR) emerges as a key technology to enhance radio spectrum utilization and provides an effective solution to meet critical spectrum demands for future mobile multimedia traffics. In this paper, we investigate reliable downlink video transmission in underlay cellular CR networks by means of cooperative diversity. We use RaptorQ code as the Application Layer Forward Error Correction scheme to combat packet loss arising from the primary user interference and other channel conditions such as channel fading. For implementing cooperative diversity, we select the best relay based on the ability of successful decoding using RaptorQ and the value of signal-to-interference-plus-noise ratio at the destination node. Moreover, for efficient primary user channel utilization, the selected relay performs merging of the encoding coefficients before forwarding to the destination. We evaluate the performance of the proposed framework under various time sharing scenarios between the direct and best indirect transmission links in terms of decoding overhead, probability of decoding failure, and peak signal-to-noise ratio of the received videos. Numerical results show that the proposed scheme outperforms the baseline transmission scheme and conventional relaying schemes using Amplify-and-Forward and Decode-and-Forward transmission techniques.</P>