Local Front Research Articles

Globalization orientation, business practices and performance outcomes: an empirical investigation of B2B manufacturing firms

Purpose This paper aims to examine how market globalization orientation (i.e. a firm’s strategic commitment to developing the target markets beyond national borders) influences business-to-business (B2B) practices to achieve competitive performance outcomes. Design/methodology/approach A conceptual framework shows how to translate strategic orientation into integrated organizational practices for competitive outcomes. A research model defines key variables (drivers, B2B practices and performance outcomes). The research model is tested using an international survey of 439 firms from four continents. And the analysis results are reported. Findings The results suggest that market globalization orientation influences organizational practices and external B2B network processes to achieve desirable performance outcomes. Integrated product development is a crucial linkage mechanism that enables firms to translate strategic network coordination and product innovation goals into improved manufacturing and firm performance. Research limitations/implications First, macro-level factors (e.g. the changing attitudes of domestic stakeholders toward globalization) do not necessarily dictate the critical aspects of the micro-level responses (e.g. firm-level practices). Despite negative narratives of globalization at the macro-level (e.g. economic inequality, unwanted immigration that spreads transmissible diseases, supply chain disruptions), firm-level responses toward global markets are determined by their missional direction and strategic priorities for achieving competitive advantage by expanding their B2B supply chains and market frontiers (Adams et al., 2019; Kobrin, 2020; Witt, 2019; Zinn and Goldsby, 2020). Second, the findings suggest that many firms take globalization orientation as an essential strategic driver that governs critical operational and network practices for achieving desirable performance outcomes. Market globalization orientation motivates B2B firms of all sizes –including small and medium-sized enterprises (SMEs) – to pursue globalization in their unique paths of differentiation. Globalization orientation expands their spheres of influence beyond their local, regional and domestic fronts. The globalization orientation of business leadership motivates firms to stretch their business frontiers without self-imposed geographical constraints. Practical implications Competitive firms choose market globalization orientation in their supply flow and implement strategic and operational practices to pursue global market opportunities. Globalization orientation is imperative to firms that seek new growth engines to achieve competitive performance that appeals to diverse market segments of the world. Social implications Outstanding firms expand their value frontiers to secure a flexible supplier base and reach out to diverse B2B customers in their domestic and global market segments. This study also suggests that firms with a market globalization orientation aim to develop novelty products, offer essential services, support the livelihood goals of people and pursue a shared vision of a sustainable planet. Originality/value In the context of conflicting societal attitudes and political priorities toward globalization, this study examines the crucial role of market globalization orientation. Using an empirical study, this paper suggests that globalization efforts succeed as firms deploy their internal and network resources to address people’s essential and timeless needs beyond national boundaries.

Experimental investigation of heat transfer characteristics of polyethylene glycol (PEG) based quench media for industrial heat treatment

Aqueous polymer quenchants are now increasingly used in the quench hardening of steels. The inverse solubility property of polymer media leads to polymer film encapsulation of the quenched component, followed by an instantaneous rupture of the polymer film. The film boiling stage is absent, thus improving heat transfer uniformity. In the present investigation, the effect of molecular weight of Polyethylene glycol (PEG) on heat transfer characteristics of PEG/water quenchants with concentrations of 5, 10, and 20 vol% was studied. The cooling curve analysis is performed to assess the cooling characteristics. Spatially dependent surface heat flux transients are estimated using the inverse heat conduction method. The rewetting kinematics is analyzed by videography and acoustic analysis of polymer film rupture during quenching. The results indicated that an increase in the molecular weight of PEG from 200 to 6000 changed the rewetting kinematics from a local wetting front movement to an instantaneous rupture of the polymer film. The change in the rewetting kinematics is reflected in the surface heat flux, indicating an increased uniformity of heat transfer. The film rupture acoustics showed that the polymer film's instantaneous breakup had a higher sound intensity than the one showing wetting front motion.

Activism and International Thought: The Women's International League of Peace and Freedom and the Problem of Statelessness in the Interwar Period

AbstractThis article examines the Women's International League for Peace and Freedom (WILPF) as an important site of women's international theorizing on the normative problem of statelessness in the League of Nations era. The problem of statelessness covered several issues connected with the loss of nationality, a new condition of human vulnerability associated with the dissolution of four empires after World War I. It opened up a series of questions about the Versailles system, where the ethical value of sovereignty was assumed, rather than examined for its consequences for individuals. WILPF developed programs of political and epistemic activity on global and local fronts that explored what it might mean to approach the statelessness question in terms of a transnational public interest, as opposed to the state interest privileged by the Versailles order. The article argues that WILPF's international thought is distinctive for the symbiotic relationship that exists between WILPF women's transnational activism and their theoretical conceptualization of the international. This is illustrated through an analysis of Jane Addams's thought, which provides a crucial link between late-nineteenth-century American pragmatism and the early twentieth-century progressive internationalism exemplified by WILPF. WILPF's interwar advocacy on the statelessness question shows how knowledge production and theory building were done in ways that are quite different to the mainstream neo-positivist idea of theory today, and which need to be included as part of our historical understanding of the origins of the twentieth-century field of international relations.

Parallel Multiobjective Multiverse Optimizer for Path Planning of Unmanned Aerial Vehicles in a Dynamic Environment with Moving Obstacles

Path planning with collision avoidance for unmanned aerial vehicles (UAVs) in environments with moving obstacles is a complex process of navigation, often considered a hard optimization problem. Ordinary resolution algorithms may fail to provide flyable and collision-free paths under the time-consumption constraints required by the dynamic 3D environment. In this paper, a new parallel multiobjective multiverse optimizer (PMOMVO) is proposed and successfully applied to deal with the increased computation time of the UAV path planning problem in dynamic 3D environments. Collision constraints with moving obstacles and narrow pass zones were established based on a mathematical characterization of any intersection with lines connecting two consecutive drones’ positions. For the implementation, a multicore central processing unit (CPU) architecture was proposed according to the concept of master–slave processing parallelization. Each subswarm of the entire PMOMVO population was granted to a corresponding slave, and representative solutions were selected and shared with the master core. Slaves sent their local Pareto fronts to the CPU core representing the master that merged the received set of nondominated solutions and built a global Pareto front. Demonstrative results and nonparametric ANOVA statistical analyses were carried out to show the effectiveness and superiority of the proposed PMOMVO algorithm compared to other homologous, multiobjective metaheuristics.

Development of late spring–early summer rainstorms in southern East Asia from the eastward propagating mid‐tropospheric cyclones of South Asia

AbstractFrom mid‐May to late June, the eastward propagation of some mid‐tropospheric cyclones (MTCs) originating in the Bay of Bengal (BOB)‐Burma (BUM) region across northern Indochina and southwest China to East Asia are observed. From 1979 to 2016, 137 MTCs were identified for the BOB‐BUM region. Eighty‐eight MTCs were trapped over northern Indochina, but 49 were propagated by the southwesterly flow of the BOB mid‐tropospheric trough to reach East Asia. Thirty‐one moved across Taiwan, but 18 did not. Eventually, all these MTCs moved to Okinawa. The former group of rainstorms produced rainfall ≥100 mm·day−1 over Taiwan, while 44 rainstorms generated rainfall ≥50 mm·day−1 over Okinawa. The 49 eastward propagating through‐Indochina MTCs exhibited the following salient features: (a) initial formation mostly occurred in the mid‐troposphere ahead/within the BOB trough in the morning over the BOB, but in the afternoon‐evening over BUM. (b) The eastward propagating BOB‐BUM MTCs underwent two descending processes: descending one mandatory level 6 hr after formation, and descending again from 700 to 925 hPa over southeastern China to interact with a low‐level cyclonic shear flow. (c) Intensified (weakened) by dipole anomalous circulation cells, the confluent monsoon southwesterly flow west (east) of Taiwan facilitated the merger of the MTC with a local front. (d) Rainfall produced by rainstorms over Taiwan/Okinawa was maintained by the intensified convergence of water vapour flux toward Taiwan/Okinawa. This hydrological process was stronger toward Taiwan than Okinawa and generated more rainfall in the former region. The impact of the BOB‐BUM MTC on East Asian weather is confirmed by this study.

Galernas: A history of coastally trapped disturbances (2003−2020) with hidden frontogenesis in the Bay of Biscay

Galerna is the term accepted for an abrupt westerly change that affects the north coast of Spain. The wind surge travels from the mid-north coast of Spain to France, generally reaching their maximum intensity at the Basque Coast, and cuts off a period of hot weather, clear skies, and calm conditions at sea. The galernas have a large history of shipwrecks and fishermen deaths. They have been characterized as coastally trapped disturbances (CTD) and their propagation, enhanced with the local formation of a micro-front, was documented to behave like a density current. Alternatively, synoptic fronts have also been reported to cause galernas, considered to be more intense than those generated by a local micro-front. In this article we have generated the first climatology (2003–2020) of these events based on an objective identification methodology. The developed Event Identification Software (EIS), based on both 10-min surface station data and hourly ERA5 reanalysis fields, together with a new Front Identification Scheme (FIS) have enabled a deeper study into the origin and development of these micro-fronts, and a more comprehensive exploration of the interaction of the oceanic fronts entering the Bay of Biscay. Our results show that the area receives an average of four to five relatively intense galernas (Vmax > 50 km h−1) per year. Their number shows a great interannual variability (from one to seven) and a marked seasonality: May and June concentrate the largest fraction (almost one episode each year) and practically no episodes in winter. They occur more frequently between noon and the late afternoon, where the most intense wind records concentrate. Very strong galernas (Vmax > 72 km h−1) have occurred in all 18 years, can happen in any month from February to November, and their monthly distribution does not show the mentioned seasonality. On the contrary, the highest rates of temperature decrease across the galerna front in the coastal stations (−∆T/0.5 h > 4 °C) do have a stronger seasonality, with May and June concentrating a relatively large number of cases with a more abrupt temperature drop. The FIS shows that most of the galernas (83.5%) have a local origin inside the Bay of Biscay, and only a few ones (16.5%) are caused by oceanic fronts initiated out of the region. The local frontogenesis is more frequently initiated by the relatively cold marine southwesterly pre-frontals preceding a parent oceanic front and blowing against the warm continentals inside the Bay of Biscay, after being ducted along the north and northwestern coast of Spain. This hidden local frontogenesis, first revealed by the FIS, seems to be enhanced by the observed lee troughing, which could have both a thermal and dynamic origin, acting simultaneously after the intense Foehn at the coastal strip, preceding the formation of the galerna front. The local front enhancement appears to be the reason for the apparent jump of the primary front, which may eventually weaken, and even disappear, as the galerna front sharpens. Even during the more occasional frontal galernas, directly caused by the westerlies or north-westerlies behind the oceanic front, their eastward propagation is more rapid over the coastal area. The front deforms in shape and may cause its characteristic unexpected/abrupt irruption. All the EIS detected galernas, even the frontal ones, are wind reversals caused by a coastally trapped marine boundary layer. The upper-level ridge over Europe, observed in all of them, seems to be a synoptic ingredient for their development, preventing the eastward propagation of Atlantic depressions and enhancing at the same time the temperature and pressure gradients between the marine and continental air masses.

Counterpropagating light in ring resonators: Switching fronts, plateaus, and oscillations

We characterize the formation of robust stationary states formed by light plateaus separated by two local switching fronts in only one of two counterpropagating fields in ring resonators with normal dispersion. Such states are due to global cross coupling and allow for frequency combs to switch from one field to the other by simply tuning the input laser frequency. Exact expressions for the distance between fronts and for plateau powers are provided in excellent agreement with simulations. These demonstrate an unusual high degree of control over pulse and plateau duration in one of the fields upon changes of one of the input laser frequencies. We identify a wide parameter region in which light plateaus are self-starting and are the only stable solution. For certain values of the detunings we find multistable states of plateaus with switching fronts, slowly oscillating homogeneous states and nonoscillating homogeneous states of the counterpropagating fields. Robustness and multistability of these unusual single-field front solutions are provided in parameter ranges that are experimentally achievable in a wide variety of ring resonators.

BOKO HARAM: SHEKAU’S DEMISE – HALCYON OR NADIR FOR SUB-SAHARAN AFRICA’S FIGHT AGAINST TERRORISM?

In Sub-Saharan Africa, no terrorist group has been as lethal as Boko Haram, under the leadership of Abubakar Shekau. Barely more than a decade, since the group’s inception, the entire Sub-Saharan Africa has been engulfed by deadly activities of the dreaded terrorist group. From evidence, more than 40,000 people have been killed, over 2 million people have been displaced, scores of forced migrants have been scattered across West Africa, properties worth billions of dollars have been destroyed, and governance in the sub-region has, essentially, been ineffective since 2009, when the group launched its violent campaign. Although there were responses both at the local front and regional front to hold back the menace of Boko Haram, these efforts were repeatedly met with repression under Shekau. However, on June 7th, 2021, there was a turn of events, as Abu Musab Al-Banawi, leader of the Islamic State of West Africa Province (ISWAP), confirmed the death of Shekau arising from a confrontation with this rival group. The question posed by this atypical occurrence is, ‘can we convincingly say Shekau’s death means the end of the road for terrorism in Sub-Saharan Africa?’ This article argues the opposite. Rejigging the memory of Mohammed Yusuf’s extermination by the police, Shekau’s influence, and the dominance of the Islamic State of West Africa Province (ISWAP), as the radical points of departure, the paper sees Shekau’s death as an alleyway for dynamic terrorism in Sub-Saharan Africa. Keywords: Shekau, Halcyon, Nadir, Lethal, Terrorism, Sub-Saharan, Africa.

Multiobjective portfolio optimization via Pareto front evolution

Portfolio optimization is about building an investment decision on a set of candidate assets with finite capital. Generally, investors should devise rational compromise to return and risk for their investments. Therefore, it can be cast as a biobjective problem. In this work, both the expected return and conditional value-at-risk (CVaR) are considered as the optimization objectives. Although the objective of CVaR can be optimized with existing techniques such as linear programming optimizers, the involvement of practical constraints induces challenges to exact mathematical methods. Hence, we propose a new algorithm named F-MOEA/D, which is based on a Pareto front evolution strategy and the decomposition based multiobjective evolutionary algorithm. This strategy involves two major components, i.e., constructing local Pareto fronts through exact methods and picking the best one via decomposition approaches. The empirical study shows F-MOEA/D can obtain better approximations of the test instances against several alternative multiobjective evolutionary algorithms with a same time budget. Meanwhile, on two large instances with 7964 and 9090 assets, F-MOEA/D still performs well given that a multiobjective mathematical method does not finish in 7 days.

Microstructure and Texture in Copper Filled Millimeter Scale Through Silicon Vias

The microstructure and crystallographic texture of copper electrodeposits in millimeter scale through silicon vias are characterized using electron backscatter diffraction. The deposits obtained from additive-containing CuSO4-H2SO4 electrolytes are characteristic of the superconformal deposition process, with growth textures and columnar grains consistent with previous findings in smaller TSV. The microstructure, like the filling evolution it records, changes substantially with chloride concentration for the concentrations of polymer suppressor used. With chloride concentrations of 80 μmol·l−1 and less, columnar grains of Cu capture the linear motion of the local growth front during filling with a strong 〈110〉 orientation along the elongated grain axes typical of deposition in chloride-containing Cu electrolytes. In the mid- and upper- via locations these columnar grains are angled upward from the sidewalls toward the center of the v-shaped growth front. In a limited region adjacent to the via bottom they extend vertically from the bottom surface. With millimolar chloride concentration, deposition also exhibits columnar grains with preferred 〈110〉 growth orientation in the lower region of the via and adjacent to the sidewalls. However, separation of the central deposit from the sidewalls results in a convex geometry of the growth front and spatially varying texture in most of the deposit.

Fully volumetric tracking of melting fronts in phase change materials with computed tomography

Recent advances in laboratory X-ray computed tomography (XCT) enabled short acquisition times on the order of a few minutes, which enable the investigation of dynamic processes in-situ by time-lapse measurements. These advances open new opportunities for revealing information on the solid-liquid phase transformation occurring in phase changes materials (PCMs), which are a promising solution for designing compact latent thermal energy storage systems (LTES). In this contribution we report results obtained from the XCT System, “LuCi”, recently installed at Lucerne university of Applied Sciences and Arts, where the evolution of the melting process in an ice cube confined within a cylindrical, X-ray transparent sample holder is tracked. Our results indicate that even tiny differences of a few percent in the density of the two different phases can be differentiated in XCT measurements. The high-power X-ray source and a fast X-ray detector of LuCi enable the acquisition of a XCT measurement in a short period (< 1 – 6 minutes). By using proper image processing methods, estimates for the volumetric melting rate, the local melting front velocity, and the tree dimensional (3D) shape of the melting front were obtained from the four-dimensional (4D) imaging data. These results will help to build more efficient thermal energy storage systems in the future, which will support the energy turnaround.

A numerical study of flow boiling in a microchannel using the local front reconstruction method

AbstractThe rapid advances in performance and miniaturization of electronic devices require a cooling technology that can remove the produced heat at a high rate with small temperature variations, as is obtained in flow boiling. To obtain insight in flow boiling, we performed numerical simulations in a 200 μm square microchannel using the local front reconstruction method. Besides validation with literature results, a parametric study shows an increasing heat removal rate and bubble growth rate with increasing wall temperature, liquid mass density, and liquid heat capacity and decreasing inlet velocity indicating the importance of phase change compared to convective transport. Finally, the heat transfer in the liquid film is studied using a Nusselt number defined with the film thickness, which is comparable to Nusselt number for falling films on hot surfaces. It is observed that convective effects are more pronounced at the bubble rear compared to the bubble front.

Investigating the roles of relative sea-level change and glacio-isostatic adjustment on the retreat of a marine based ice stream in NW Scotland

The record of ice-sheet demise since the last glacial maximum (LGM) provides an opportunity to test the relative importance of instability mechanisms, including relative sea-level (RSL) change, controlling ice-sheet retreat. Here we examine the record of RSL changes accompanying the retreat of the Minch Ice Stream (MnIS) of northwest Scotland during the deglaciation following the LGM as well as use the record to provide additional age constraints on a local late-glacial readvance known as the Wester Ross Readvance. We use new and existing records of RSL change obtained from isolation basins in Wester Ross along the flanks of the former MnIS to test available glacial-isostatic adjustment (GIA) predictions of the deglacial RSL history for the region. Using these GIA model predictions we examine the nature of RSL change across the retreating front of the MnIS through the early deglaciation. Our new radiocarbon ages from these basins confirm the timing of deglaciation within the inner trough of the former MnIS as well as refines the age of the Wester Ross Readvance, both established by earlier cosmogenic-based studies. We find that the Wester Ross Readvance culminated around 15.8 ± 0.1 ka, slightly earlier than recent suggestions. Near Gairloch, Wester Ross, RSL fell from a marine limit ∼20 m above present at ∼16.1–16.5 ka. Three isolation basins record RSL fall over the following ∼0.8 ka allowing a comparison between GIA predictions and RSL observations. Our new analyses suggest that the rate of RSL rise increased at the ice front, in concert with the MnIS encountering a landward sloping bed potentially aiding the rapid retreat of the MnIS from 17.6 to 16.4 ka BP. This observation suggests that GIA during deglaciation does not necessarily induce a stabilizing RSL change to marine-based ice streams as some models have suggested. Along indented ice margins, the RSL field at the front of individual ice streams may be governed by the regional GIA signal driven by the ice sheet as a whole, rather than the local ice front. In addition, the stabilizing impact of post-glacial rebound is dependent on an Earth rheology weak enough to respond quickly to the ice-sheet retreat. In the case of the MnIS, the RSL experienced at the front of the ice stream was likely governed by the earlier ice mass extent, the larger ice masses lying to the east and south of the highly indented ice front, and the relatively strong Earth rheology beneath the British Isles. Thus, the geometry of the ice sheet margins, such as those in Greenland and Antarctica today, and the Earth rheology beneath them need to be taken into account when considering the stabilizing impact of post-glacial rebound on marine ice sheet retreat.

Effects of melt convection on stray grain formation in single crystal superalloys during directed energy deposition

During laser repairing of Ni-based single crystal (SX) superalloys, stray grain (SGs) formation leads to a deterioration of high-temperature properties and hot cracking. The main goal is to prevent SGs formation from forming, which controls the local solidification front thermal gradient ( G ) and solidification velocity ( V ). Meanwhile, the melt pool geometry, which is influenced by melt convection, has a significant impact on G and V . Here, experiments and theoretical calculations were used to study the evolution of the melt pool geometry during melt convection and its effects on the formation of SGs. Melt convection, i.e., Marangoni convection, outperformed thermal conduction in the SX superalloys melt pool during directed energy deposition, as evidenced by the estimated Peclet number and Prandtl number. The integrative impact of laser power, scan velocity, and beam diameters exacerbated Marangoni convection as the laser energy density distribution increased. Marangoni convection caused the melt pool shape to change from a near-semicircle to an undulating morphology, promoting the oriented-to-misoriented crystal growth transition and resulting in high stray grain sensitivity. The heat and mass transport in front of the dendrite tips was altered by Marangoni convection, which aggravated the deviation of the epitaxial dendrite orientation with respect to the substrate. This work provides an in-depth insight into controlling SG formation during additive manufacturing of SX superalloys. • The melt pool geometry transformed from a near semicircle to an undulating morphology by Marangoni convection. • The interaction between the thermal conduction and thermal convection was calculated for SX superalloys. • The mechanism of the melt pool geometry evolution resulting from Marangoni convection was proposed. • Marangoni convection promoted the oriented-to-misoriented transition leading to high sensitivity of stray grains. • Marangoni convection aggravated the epitaxial growth deviation by altering the heat and mass transfer.

Thermally activated intermittent dynamics of creeping crack fronts along disordered interfaces

We present a subcritical fracture growth model, coupled with the elastic redistribution of the acting mechanical stress along rugous rupture fronts. We show the ability of this model to quantitatively reproduce the intermittent dynamics of cracks propagating along weak disordered interfaces. To this end, we assume that the fracture energy of such interfaces (in the sense of a critical energy release rate) follows a spatially correlated normal distribution. We compare various statistical features from the obtained fracture dynamics to that from cracks propagating in sintered polymethylmethacrylate (PMMA) interfaces. In previous works, it has been demonstrated that such an approach could reproduce the mean advance of fractures and their local front velocity distribution. Here, we go further by showing that the proposed model also quantitatively accounts for the complex self-affine scaling morphology of crack fronts and their temporal evolution, for the spatial and temporal correlations of the local velocity fields and for the avalanches size distribution of the intermittent growth dynamics. We thus provide new evidence that an Arrhenius-like subcritical growth is particularly suitable for the description of creeping cracks.

The collective effect of finite-sized inhomogeneities on the spatial spread of populations in two dimensions.

The dynamics of a population expanding into unoccupied habitat has been primarily studied for situations in which growth and dispersal parameters are uniform in space or vary in one dimension. Here, we study the influence of finite-sized individual inhomogeneities and their collective effect on front speed if randomly placed in a two-dimensional habitat. We use an individual-based model to investigate the front dynamics for a region in which dispersal or growth of individuals is reduced to zero (obstacles) or increased above the background (hotspots), respectively. In a regime where front dynamics is determined by a local front speed only, a principle of least time can be employed to predict front speed and shape. The resulting analytical solutions motivate an event-based algorithm illustrating the effects of several obstacles or hotspots. We finally apply the principle of least time to large heterogeneous environments by solving the Eikonal equation numerically. Obstacles lead to a slow-down that is dominated by the number density and width of obstacles, but not by their precise shape. Hotspots result in a speed-up, which we characterize as function of hotspot strength and density. Our findings emphasize the importance of taking the dimensionality of the environment into account.

Void content reduction of composites with sensor-aided injection strategy in liquid composite molding process

Void is one of the critical issues affecting the mechanical performance of fiber-reinforced polymer composites. Aiming at the composite parts formed by Liquid Composite Molding, this develops a sensor-aided injection strategy, including a real-time online monitoring module and a sensor-aided injection system, which realizes continuous detection of resin flow and the automatic injection flow rate adjustment to minimize void content. Flow front profile continuously recorded by the monitoring module in resin flow direction is reconstructed in real-time. It provides a digital representation of the saturation state of the fibrous preform, which is referred to Digital Process Twin (DPT) in present work. The local flow front velocity is then extracted from the DPT, thus the sensor-aided injection system can maintain the flow front velocity at a optimal level, regardless of the cross-sectional geometry. Experimental investigation confirms the representative of DPT to actual flow. Characterization of void content by micro-computed tomography shows that the proposed sensor-aided injection strategy not only effectively decreases the void content from 0.32%, 0.34%, and 0.79% to 0.18%, 0.18%, and 0.19%, but also significantly improves the part quality consistency. Furthermore, to the best knowledge of the authors, This work is the first to use micro CT to investigate the effect of velocity on void content from the mesoscopic and microscopic scales, although the topic has been widely investigated theoretically.

Influence and variability of monsoon trough and front on rainfall in Thailand

AbstractHigh variabilities in rainfall and the subsequent consequences have caused severe water‐related issues for Thailand over recent decades. In this study, the factors that affect rainfall variability over Thailand were determined. The spatio‐temporal structures of the monthly rainfall in Thailand between 1979 and 2018 were extracted via an empirical orthogonal function (EOF) analysis. With a unimodal temporal structure, the first EOF mode suggests the overall phenomenon governing rain characteristics in Thailand. The higher modes, consisting of bimodal temporal structures, indicate different rain phenomena in various regions. A significantly high correlation between the 3‐month average of the monsoon trough index and rainfall was observed, while wet adiabatic front and convective available potential energy (CAPE) data had a moderately high correlation. Only the local front index, within the Gulf of Thailand, correlated to the rain characteristics along the east coast of southern Thailand. The cross‐wavelet analysis indicated that most of the rainfall variability correlates with monsoon trough. However, the front can involve extreme events. The interannual variability of monsoon trough and rainfall with a dominant time scale between 3.0 and 6.0 years has significantly increased since 1995. Meanwhile, the intra‐annual variability is more intermittent, indicating rare intensified strong tropical cyclones along the monsoon troughs in Thailand. The interannual variability of the monsoon trough and front indices also intermittently connects with the Southern Oscillation Index (SOI). However, the relationship in annual and intra‐annual cycles is mostly weak. Therefore, the dependence of interannual variability of rainfall in Thailand on SOI or monsoon trough is comparable. Notably, the intra‐annual rainfall variability is heavily influenced by the monsoon trough and front. This study is the first to identify the crucial factors behind the seasonal rain phenomena in Thailand. This information will benefit seasonal rainfall predictors and increase preparedness for hydro‐climatic related disasters in the Indo‐China region.

Flame Structure Characterization in a Dual-Mode Scramjet Using Hydroxyl Planar Laser-Induced Fluorescence

The flame front of a premixed ethylene–air turbulent flame in a high-speed flowfield was imaged using hydroxyl radical (OH) planar laser-induced fluorescence (PLIF). An electrically heated continuous flow facility produced inflow conditions with a total temperature of 1200 K, corresponding to a flight Mach number of about five. A statistically stationary turbulent flame stabilized over a scaled-down cavity was used to generate experimental data for future comparisons with direct numerical simulations. A laser sheet with a wavelength of 283.55 nm was used to excite the (8) transition of OH. The sheet waist had a full width at half-maximum of . Two-dimensional OH-PLIF images were collected at high in-plane spatial resolution (approximately ) with a field of view of . The images spanned a region of along the spanwise centerplane. The local OH gradient was used to isolate the flame front in all images through an automated process. Each image was processed to obtain the appropriate statistics, time-averaged flame surface density, and flame front curvature values. The distribution of local flame front curvature values was approximately constant across the domain.

Bayesian inversion algorithm for estimating local variations in permeability and porosity of reinforcements using experimental data

A novel Regularising Ensemble Kalman filter Algorithm based on the Bayesian paradigm was applied to RTM processes to estimate local porosity and permeability of fibrous reinforcements using measured values of local resin pressure and flow front positions during resin injection. The algorithm allows to detect locations of defects in the preform. It was tested in virtual experiments with two geometries, a two-dimensional rectangular preform and a more complex 3D shape, as well as in laboratory experiments. In both the virtual and laboratory experiments, it was demonstrated that the proposed methodology is able to successfully discover defects and estimate local porosity and permeability with good accuracy. The algorithm also provides confidence intervals for the predictions and estimations of defect probabilities, which are valuable for analysis of the process.