Gap Zone Research Articles

Serial Quantitative Evaluation of Load Redistribution and Osteotomy Gap After Medial Open-Wedge High Tibial Osteotomy.

The goal of medial open-wedge high tibial osteotomy (MOW-HTO) is to redistribute load by realigning the lower limb. This surgery is indicated for mild to moderate medial compartment osteoarthritis with varus deformity in cases unresponsive to conservative treatment. Procedures for accompanying cartilage lesions, such as multiple drilling on the medial femoral condyle (MFC), are often performed simultaneously, potentially affecting bone metabolism along with load redistribution and union progression. This study assessed changes in bone metabolism following MOW-HTO. Two-year follow-up data were collected from 51 knees undergoing MOW-HTO between March 2019 and December 2020. Single-photon emission computed tomography and conventional CT (SPECT/CT) were performed on postoperative Day 1, 3 months, 1 year, and 2 years. Maximum standardized uptake value (SUVmax) was measured in each compartment and the osteotomy gap. At 1 year postoperatively, SUVmax decreased in the medial femur and tibia zones (p < 0.001). SUVmax decreased in the lateral osteotomy gap zones at 1 year (p = 0.001 anterior; p = 0.002 posterior), while medial zones showed a sustained increase. At the posteromedial zone, SUVmax decreased at 2 years (p = 0.012). Subjects were divided into two groups: those with MFC drilling (group one) and those without (group two). SUVmax was higher in group one throughout the 2 years (p < 0.001). Unloading effects were notable in the medial compartment. MFC drilling increased SUVmax, creating different patterns between groups. SUVmax decrease in the osteotomy gap occurred earlier in the lateral zone.

Flow-induced vibrations of staggered circular cylinders

The flow-induced vibrations (FIVs) of staggered two-degree-of-freedom cylinders with a constant streamwise offset (L/D = 2, L is the streamwise spacing between the cylinders of diameter D) and varying cross-stream offset (0 ≤ S/D ≤ 5, S is the cross-stream spacing) were numerically simulated. The effects of S/D on the in-line and cross-flow vibrations, flow fields, distributions of the surface pressures, and the energy properties were comprehensively investigated to study the characteristics of the FIVs. The upstream cylinder primarily experiences vortex-induced vibrations (VIVs), while distinct FIVs of the downstream cylinder occur when S/D ranges from 0 to 3, and the flow characteristics vary with the reduced velocity (Vr) and S/D. When Vr = 3, vortex pairs along with reverse-flow reattachment are observed within the gap zone at small S/D. The pressures on the downstream cylinder become asymmetric due to the vortex strong interactions. When Vr = 7 and 11, a merging vortex emerges and moves closer to the rear surface of the downstream cylinder with increasing S/D, which increases negative pressure on the lower part of the downstream cylinder, further influencing the promoting effect of the merging vortex on structural vibrations. Moreover, when S/D ≥ 3, the effects of the upstream cylinder on the downstream cylinder diminish. Both cylinders exhibit identical vibrations and wake patterns, and the mean power distribution on the downstream cylinder becomes symmetrical with a magnitude similar to that of the upstream cylinder, which can be considered as two independent cylinders undergoing VIVs.

Dynamics of N-elastically longitudinal coupled rotating pendulums with smooth and discontinuous nonlinearities: Generation of chaotic bursting with many orbits as a solution

The dynamics of a mechanical network, consisting of a certain number (N) of cells, in which each unit cell consists of the irrational coupling of a simple pendulum and inclined mass-spring oscillator, is investigated. The single cell was recently introduced by Ning Han and Qingjie Cao, and it has strong irrational nonlinearity, exhibiting smooth and discontinuous characteristics due to the geometry configuration. The obtained network has a large degree of freedom and consequently has richer dynamics as compared to a single one. The set of discrete equations of this network is found, while the first equation is driven by an external sinusoidal force; the variables here are the angles between the vertical direction and the directions of mass in each unit cell. By using the non-driven version of this set of equations, the equilibrium points are found as well as their stability using the Jacobian matrix. Then, by using the multiple time scale method, the solutions of the set of the network equations are found for weak amplitude oscillations of the system, while the large amplitude solutions are found numerically, showing the ability of the network to transform the shape of some solutions at the input to other forms as the signals evolve in the network. One notices the generation of simple chaotic signals as well as the train of impulse signals. What is important here is the generation of the chaotic bursting with many orbits by the system, which are the simultaneous oscillations around several fixed points. For the case of numerous cells, the system can be used as a waveguide; this is why the set of the equation of the network is reduced to the extended complex Ginzburg Landau (ECGL) equation, with complex nonlinear dispersion and nonlocality terms, using the Tanuiti's reduction perturbation methods. The dissipative dark compacton and peakon as solutions for the ECGL equation are then found. The input-output matching of the network is next investigated via the transfer function of the system near the equilibrium points. The inverse Fourier transform of the transfer function multiplied by the Fourier transform of the input sinusoidal force gives the solution of the network equation for low amplitude oscillations. Finally, the supratransmission condition is studied, leading to the fact that the input sinusoidal signal with frequency nearly inside the forbidden gap zone gradually transforms into the train of chaotic bursting.

Analisis Deformasi di Lampung dan Selat Sunda berdasarkan Data GNSS tahun 2018 hingga 2021

The Lampung Province and Sunda Strait have a seismic gap zone with the potential for major earthquakes in the future. This study analyzes the deformation occurring in this region using continuous Global Navigation Satellite System (GNSS) station data from Indonesia Continuously Operating Reference Station (InaCORS) and Sumatran GPS Array (SuGAr) from 2018 to 2021.5. The GNSS data was processed using the Bernese 5.2 scientific software, applying least squares for velocity changes and statistical tests to analyze significance. The data processing was carried out in two schemes: the first scheme covering 2018-2020, and the second covering 2019-2021. The results of the deformation analysis from 2018 to 2021, using two continuous GNSS data processing schemes, showed velocity changes relative to the Sundaland Plate ranging from ~2 mm/year to ~20 mm/year. In the eastern region of the Sumatra fault, the velocity changes were smaller, around ~5 mm/year, due to the minimal influence of tectonic activity. However, in the Sunda Strait region, the deformation was influenced by volcanic activity. The deformation occurring in Lampung Province and the Sunda Strait, based on GNSS velocity changes, significantly contributes to tectonic and volcanic activities.

Study on the design of gas extraction drilling angle of crossing coal layer drilling in the floor rock roadway considering the boreholes superposition effect

To solve the problem of the borehole design for extracting gas of crossing coal layer drilling in the floor rock roadway and to improve the efficiency of drilling arrangement as much as possible under the premise of eliminating the gap zone of extraction, the formula for calculating the optimal arrangement angle of crossing coal layer drilling in the floor rock roadway was put forward, and the difference of the superposition effect of the holes on the radius of the effective extraction area under the different arrangement modes and spacings was analyzed through numerical simulation. The experimental results show that the optimal angle, volume, and other calculation formulas for drilling arrangement are consistent with the CAD calculation values, verifying the correctness of these calculation formulas. The study discusses the coefficients of variation of effective extraction radius (R) for three types of arrangement, different drill spacing, and the time to reach the two coefficients of variation, 1.05 and 1.03, as a criterion for whether or not to consider the effect of borehole superposition. The results of the tests can provide borehole designers with calculation formulas and provide theoretical references for the R differences that need to be considered in different scenarios.

Shallow Structure and Seismic Amplification Effects in the Weifang Segment of the Tanlu Fault Zone Based on the Spectral Ratio Method

Abstract The Weifang segment of the Tanlu fault zone (TLFZ) is located in the central section of the TLFZ, eastern China, and has been identified as an earthquake gap zone. Previous studies in the region have mainly focused on the crustal velocity structure and anisotropy, with limited attention to the shallow near-surface structures. In this study, we analyzed the distribution of sediment thickness and evaluated the seismic amplification effects in the Weifang segment of the TLFZ using the horizontal-to-vertical spectral ratio (HVSR) method and the standard spectral ratio (SSR) method. The data we used are from a dense array of 302 three-component seismometers deployed in 2017 for three months. The lowest peak frequency of HVSR indicates that the northwestern part of the study area exhibits relatively thicker sedimentary deposits, estimated to be 800–1200 m in thickness, consistent with both tomographic and geological studies. The SSRs are calculated from 43 regional and teleseismic earthquakes with respect to 12 reference stations. The results from SSR show strong amplification in the 0.2–2 Hz frequency range for sites on the northwestern part, and the amplitude can be up to 15 times larger than that of the bedrock site. We also find significant amplification effects as well as thick sedimentary layers at specific stations along the eastern branch of the TLFZ, suggesting a localized low-velocity zone along the fault. Our results also demonstrate that using the single-site seismic method can provide new constraints on the fine structure and site responses of the fault zone, which are important for seismic hazard assessment.

Correlation of digital twin and roll surface sensor results for AZ31 alloy TRC process

Due to the growing interest in lightweight constructions, the continuous casting of nonferrous metals is continuously developing as a result of the cost-effectiveness of this process, which combines several stages of sheet production. Unfortunately, because of the characteristics of the process, the parameters in the roll gap, such as, for example, pressure and temperature, are unknown, significantly affects the understanding of the phenomena occurring in the material during rolling. Therefore, at IMF Freiberg, a sensor consisting of a piezo sensor and two thermocouples measuring the temperature at two different heights was mounted on the surface of the roll, making it possible to control the process parameters live during the TRC trial. The measurements were further supported by a digital twin in the form of a layer model, combining a viscous and solid region for each layer in a single tool. The computations in this tool are performed offline and the computation time is in the order of seconds, thus much less than that of the finite element method. Because the layer model measures the temperature of the magnesium strip, FEM simulations were used to validate measurements from thermocouples. Experimental results have been obtained that allow for a direct correlation between the development of the pressure and temperature and the length of the fully solidified LD part in the roll gap zone, which correlates directly with the effective total equivalent strain. Using the sensor and layer model, it is possible to train a digital twin that can be used for online estimation of the final strip properties obtained in the TRC process.Graphical abstract

Numerical study on the cooling performance of various arrangements of medium-gap-medium for direct evaporative cooling systems

Medium is one of the most critical components in direct evaporative cooling systems. The current study is to investigate the effect of various arrangements of medium-gap-medium (MGM) on the performance of direct evaporative cooling systems, and to find the most practical MGM arrangement for engineering application. Different widths of medium 1 zone, gap zone and medium 2 zone are extensively studied by numerical simulation. Results indicate that: (1) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 79.8% to 91.9% and from 14.30 Pa to 14.76 Pa, respectively when the width of gap zone increases from 50 mm to 300 mm; (2) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 83.8% to 93.5% and from 14.42 Pa to 25.04 Pa, respectively when the width of medium 1 zone increases from 100 mm to 250 mm; (3) the cooling efficiency and air-side pressure drop at air speed of 1.5 m·s−1 increase from 84.1% to 93.9% and from 14.40 Pa to 25.05 Pa, respectively when the width of medium 2 zone increases from 50 mm to 200 mm; (4) the cooling efficiency gradually tends to its maximum when the sum width (the total width of medium 1 zone, gap zone and medium 2 zone) reaches to 350 mm. Finally, the arrangement of 150 mm medium 1 zone, 100 mm gap zone and 100 mm medium 2 zone is found to be the most practical MGM arrangement.

Ultrastructure and Nanoporosity of Human Bone Shown with Correlative On-Axis Electron and Spectroscopic Tomographies.

Mineralized collagen fibrils are the building block units of bone at the nanoscale. While it is known that collagen fibrils are mineralized both inside their gap zones (intra-fibrillar mineralization) and on their outer surfaces (extra-fibrillar mineralization), a clear visualization of this architecture in three dimensions (3D), combining structural and compositional information over large volumes, but without compromising the resolution, remains challenging. In this study, we demonstrate the use of on-axis Z-contrast electron tomography (ET) with correlative energy-dispersive X-ray spectroscopy (EDX) tomography to examine rod-shaped samples with diameters up to 700 nm prepared from individual osteonal lamellae in the human femur. Our work mainly focuses on two aspects: (i) low-contrast nanosized circular spaces ("holes") observed in sections of bone oriented perpendicular to the long axis of a long bone, and (ii) extra-fibrillar mineral, especially in terms of morphology and spatial relationship with respect to intra-fibrillar mineral and collagen fibrils. From our analyses, it emerges quite clearly that most "holes" are cross-sectional views of collagen fibrils. While this had been postulated before, our 3D reconstructions and reslicing along meaningful two-dimensional (2D) cross-sections provide a direct visual confirmation. Extra-fibrillar mineral appears to be composed of thin plates that are interconnected and span over several collagen fibrils, confirming that mineralization is cross-fibrillar, at least for the extra-fibrillar phase. EDX tomography shows mineral signatures (Ca and P) within the gap zones, but the signal appears weaker than that associated with the extra-fibrillar mineral, pointing toward the existence of dissimilarities between the two types of mineralization.

Effect of climate and habitat on morphological characteristics and fruit production of Picralima nitida (Stapf) in West Africa

Picralima nitida is an important African medicinal plant species used in pharmaceutical industries and traditional medicine to treat several diseases. Despite its importance, the species faces conservation problem. This study evaluated the effect of climate and habitat on morphological characteristics and fruit production of P. nitida. A total of 132 fruiting trees was randomly sampled from three habitat types (home gardens, botanical garden and natural forest) and three soils (Nitisols, Arenosols and Acrisols) in Dahomey Gap and Guineo-Congolese zone. A total of 5 morphological traits and fruit production were recorded per tree to describe the relationship between morphological determinism of the species and climate. Pearson correlation was performed to identify the suitable habitat type in each climatic zone. Harmonized World Soil Database was used to determine physicochemical characteristics of the soil types on which the species occurred. Results revealed that the climatic zones (p&lt;0.001) and habitat types (p&lt;0.0001) influenced significantly the morphological characteristics and fruit production of P. nitida. High trees with more number of fruits were observed in home gardens on acid soils (Nitisols (pH: 5) and Arenosols (pH: 5.3)) in Dahomey Gap. In Guineo-Congolese zone, the species was more present in natural forest on acid Acrisols (pH: 5).

Thermal Control Investigations on Separation Zone of Ceramic Thermal Protection System

Ceramic thermal protection system (TPS) is bonded to the skin of a hypersonic vehicle through a strain isolation pad, and the separation of the TPS will affect the safety of the vehicle. In this paper, the aeroheating of the separation zone for the ceramic TPS is studied and compared with that of the intact TPS. The intact TPS mainly considers the aeroheating of the gap. The heat flux increases sharply in both the gap and separation zone, especially on the windward wall. The difference of peak heat flux between the windward and leeward walls in the separation zone is much larger than that in the gap, and the heat flux away from the gap and separation zone gradually returns to the normal heat flux of the TPS. The heat flux in the gap only exists in the small zone of the upper part, whereas that in the separation zone is widely distributed on the side walls. The heat flux on the bottom of the gap approaches zero, whereas that of the separation zone is high in the middle and low at ends, and the heat flux in the middle reaches 55% of the normal heat flux of the TPS. In addition, an analysis of influencing factors is conducted.

Sedimentary Records of Liquefaction: Implications From Field Studies

AbstractThe susceptibility of grains in sediment to the liquefaction process causes the development of deformation structures. Some sediments undergo liquefaction, others do not. There is a group of sediments especially prone to liquefaction, which was proven during laboratory experiments. However, the field results are often slightly different from those obtained experimentally because of many unpredictable factors influencing the course of the liquefaction process. For this reason, we tested 144 samples of unconsolidated Quaternary‐age sediments, collected from eight study sites in Germany, Lithuania and Latvia, which have been liquefied. We also present some new dating results. These samples were divided into two groups of soft‐sediment deformation structures: concave up (e.g., injection structures) and concave down (e.g., load casts, pseudonodules). The granulometry of all deformation types was statistically evaluated, which allowed identifying textural differences between sediment contained in concave up and concave down structures. We suggest that the mobilization of silt fraction is responsible for the further deforming process. We also confirm that the maximum content of clay in sediment prone to liquefaction cannot exceed 14%, but only with a significant content of coarser fractions (silt and sand). Moreover, we identified two separate zones of the specific grain size in which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third “transitional zone” where all forms occur. The “transitional zone” is separated from the concave up structures and concave down structures zones by two “gap zones” in which no liquefied sediments were observed.

Role of carboxylic organic molecules in interfibrillar collagen mineralization.

Bone is a composite material made up of inorganic and organic counterparts. Most of the inorganic counterpart accounts for calcium phosphate (CaP) whereas the major organic part is composed of collagen. The interfibrillar mineralization of collagen is an important step in the biomineralization of bone and tooth. Studies have shown that synthetic CaP undergoes auto-transformation to apatite nanocrystals before entering the gap zone of collagen. Also, the synthetic amorphous calcium phosphate/collagen combination alone is not capable of initiating apatite nucleation rapidly. Therefore, it was understood that there is the presence of a nucleation catalyst obstructing the auto-transformation of CaP before entering the collagen gap zone and initiating rapid nucleation after entering the collagen gap zone. Therefore, studies were focused on finding the nucleation catalyst responsible for the regulation of interfibrillar collagen mineralization. Organic macromolecules and low-molecular-weight carboxylic compounds are predominantly present in the bone and tooth. These organic compounds can interact with both apatite and collagen. Adsorption of the organic compounds on the apatite nanocrystal governs the nucleation, crystal growth, lattice orientation, particle size, and distribution. Additionally, they prevent the auto-transformation of CaP into apatite before entering the interfibrillar compartment of the collagen fibril. Therefore, many carboxylic organic compounds have been utilized in developing CaP. In this review, we have covered different carboxylate organic compounds governing collagen interfibrillar mineralization.

Performance of rubber-concrete composite periodic barriers applied in attenuating ground vibrations induced by metro trains

Recently, the use of periodic vibration isolation barriers (PVIBs) has emerged as a significant method for attenuating environmental vibrations along the propagation path. Previous studies have indicated that periodic infilled trenches and piles can effectively isolate low-frequency surface waves. However, a considerable number of these periodic structures require full-size shipments or cast-in-place construction, thus increasing the shipment difficulty or construction period. In addition, few experimental studies have reported on the performance of PVIBs under underground excitation. To solve these problems, this study proposes a novel periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics. A laboratory test was performed, in which the calculated frequency band gap (FBG) and attenuation zones of the optimised PCRCB were validated under ground-borne and underground hammering excitations. Then, a numerical model was developed to analyse the vibration mitigation effect of the optimised PCRCB considering the metro train loads. The results of the laboratory study demonstrated that the depth of the impact load affects ground vibration attenuation. The optimised PCRCB has been proven to exhibit good vibration isolation performance. The results of the numerical study demonstrate that the vibration mitigation effect of the PCRCB on the ground surface is good under underground metro train loads. The insertion loss (IL) increases, but its value is less than 2 dB, with the ratio of burial depth to tunnel base depth increases from 1 to 2 times. Accordingly, the ratio of the burial depth to the tunnel base depth is recommended to be 1 in the vibration isolation project of an underground metro train.

Numerical modelling of plate anchors under sustained load: The enhancement of capacity from consolidation

Embedded plate anchors can be used to moor floating offshore facilities. In taut mooring systems, a sustained tension carried by the anchors affects their long-term capacity due to consolidation effects in the soil surrounding the anchor. The resulting gain in capacity provides a potential basis for more efficient anchoring system design. To quantify this effect, and to understand the underlying mechanism, a systematic numerical study has been performed, to capture the effect of sustained loading and consolidation on soil failure mechanisms around an embedded plate anchor. The modified Cam clay model is used, to capture the effect of consolidation on soil strength, and also to faithfully model the process by which a water-filled gap forms under the plate, due to a loss of contact between the plate and the soil, with seepage into the gap zone. A critical observation is the load transfer process when such a gap forms beneath the plate after the applied tension causes the effective stress to fall to zero. The formation of this gap is shown to depend, in a systematic way, on the sustained tension, or preload, the soil strength ratio, the relative sharing of the anchor load between compression above the plate and tension below, as well as the embedded depth of the anchor. Simple relationships that capture these mechanisms are provided, linking the net change in soil strength above and below the anchor to the change in undrained capacity. As an example, it is shown that in soft normally-consolidated clays, a sustained preload of 60 % of the initial capacity, can create a 25 % gain in capacity, at which point the factor of safety is raised from 1/0.6 = 1.67 to 2. This gain is only available for anchors embedded by more than twice their diameter. At shallower embedment, the loss of strength in the unloaded soil beneath the anchor outweighs the gain in strength in the smaller zone of soil above the anchor, and the consolidation process causes a net weakening.

Hydronic flow path analysis on the thermal comfort performance of radiant cooling system

Construction and operation in the building sector account for more than 1/5th of global energy consumption. Moving on to an energy-efficient cooling technology and eco-friendly building material can lead to energy savings and a reduction in associated CO2 emissions. In the present study, an energy-efficient thermally activated building system (TABS) is integrated with eco-friendly building material, namely, glass fibre reinforced gypsum (GFRG). The proposed hybrid system is termed as thermally activated glass fibre reinforced gypsum (TAGFRG) system. This system is not only energy-efficient and eco-friendly but also provides better thermal comfort. An experimental room is constructed with the TAGFRG roof within the Indian Institute of Technology Madras campus, Chennai, i.e., in a tropical warm and humid climate zone. The TAGFRG roof has reinforcement in every third cavity with cooling pipes, while in the other two cavities, cooling pipes are embedded with air gap and partial reinforcement. The TAGFRG roof has four parallel loops of cooling pipelines, and each loop consists of one reinforcement zone (RZ) and two air gap zones (AZ1 and AZ2) in series. According to the water flow path in a single loop, various combinations of the flow path, i.e., RZ → AZ1 → AZ2, AZ1 → RZ → AZ2 and AZ1 → AZ2 → RZ, have been analyzed. According to the adaptive thermal comfort model, the water flow path has a negligible effect on thermal comfort. The average operative temperature for all the cases investigated varies between 28.1 and 29.2 °C. The operative temperature is always within the 90% band of thermal comfort, as per the adaptive comfort model.

Apparent Low‐Velocity Belt in the Shallow Anninghe Fault Zone in SW China and Its Implications for Seismotectonics and Earthquake Hazard Assessment

AbstractThe Anninghe fault forms the eastern boundary of the Sichuan‐Yunnan block in Southwest China and has been identified as an earthquake gap zone. This study intends to construct the upper crustal shear wave velocity (Vs) structure beneath the Anninghe fault to understand its seismotectonics and potential large earthquake hazards. We deployed a dense seismic array along the southern central Anninghe fault valley. From the 3‐month continuous records, we calculated vertical‐component cross‐correlation functions (CCFs). However, the surface wave signals in the CCFs are intensely interfered by near zero‐time‐lag noise. We proposed a mode separation method based on the high‐resolution linear Radon transform, which suppressed the interfered noise and greatly enhanced the surface wave signals for ambient noise tomography of the Vs structure. The fine upper crustal structure reveals a distinct narrow low‐velocity belt within a depth of 3 km beneath the Anninghe fault zone. At deeper depths (4.5–8 km), the narrow low‐velocity belt shifts to the east and correlates with the distribution of local earthquakes. Combining previous results with our new findings, we presented a seismotectonic model of the southern central Anninghe fault, which interprets the narrow low‐velocity belt as a water‐contained fracture zone that forms a seismogenic zone at deeper depths under transpression. In addition, we demonstrated through scenario earthquake simulations that fine structures play a significant role in the assessment of earthquake hazards along the Anninghe fault. As such, this study provides a typical window into seismotectonics and large earthquake hazards in the active southeastern Tibetan Plateau.

Performance simulation and key parameters in-plane distribution analysis of a commercial-size PEMFC

Commercial fuel cell stacks often have a large electrode area to obtain a high power output. Uniformity in-plane distribution of vital physical quantities plays a key role in improving cell performance and avoiding degradation. In this study, a three-dimensional two-fluid multiphase model is adopted to analyze the in-plane distribution characteristics of key parameters (reactant concentration, temperature, local current density, and membrane water content) for a large-scale PEMFC with an active area larger than 300 cm2. The particular feature of the PEMFC studied is that there are gap zones near the edge between the bipolar plate and gas diffusion layer and membrane. The results show that for the structure without gap zones, the cell performance improved by about 1%. The non-uniformity of cathode reactant distribution is generally higher than that of the anode; The non-uniformity of temperature in the x direction is higher than that in the y direction (flow-direction). With the increase of average current density, the temperature in the membrane increases, and the membrane dehydrates gradually. The flow direction of coolant has a significant impact on the cell performance. When coolant is in the same direction as hydrogen, the cell performance decreases by about 3.75% at 0.8 A/cm2.

Estimation of B-Value Variation as Earthquake Precursor in Java Region with Maximum Likelihood Method

Java Island is one of the areas with a population density of 1,171 people/km2, which is relatively high compared to other regions in Indonesia. The tectonic setting of the Java region is affected by the interaction of tectonic plate subduction between the Indo-Australian Plate and the Eurasian Plate which moves at the rate of 67 mm/year. In addition, the presence of several active faults on Java Island also contributes to the tectonic setting. The implication of this setting is a relatively high level of potential earthquake events and some of them are destructive earthquakes. The estimation of b-value variations by using Gutenberg-Richter Equation plays an important role in estimating the occurrence of earthquakes. The aims of this study are to determine the role of spatial and temporal variations of b-value as earthquake precursors on Java Island. In this research, earthquakes analysis was carried out in the form of spatial and temporal variations of b-value from earthquake catalog data in 1900-2016 for the Java Island region. Based on the estimation of earthquake recurrence time for magnitude 6.5, 7, and 7.5, and also the analysis of spatial variation of b-value shows the areas with the potential for significant earthquakes in the west and eastern part of Java region. In addition, our result also obtains the existence of a seismic gap zone in the southern part of Central Java.

Numerical simulation of evaporative cooling process in a medium-gap-medium arrangement

Wet medium is the key components of direct evaporative cooling system, and its performance affects the cooling performance extensively. The medium arrangement contributes much to good cooling performance of direct evaporative cooling system. The current paper continues previous experimental study of medium-gap-medium arrangement of wet medium, aiming to investigate the heat and mass transfer mechanism in such novel arrangement. A 3-D model was established using Fluent 18.0 to simulate the heat and mass transfer process in medium-gap-medium arrangement of wet medium. The airflow field, air temperature, humidity distribution and pressure drop were explored. The effects of the widths of the air gap, ambient dry-bulb temperature, wet-bulb temperature, and air speed on the cooling performance of medium-gap-medium arrangement were studied. Simulation based on the condition of air dry-bulb temperature of 27 °C, wet-bulb temperature of 19 °C, air speed of 1.5 m s−1, finds that: (1) the air temperature drops flowing through the 100 mm medium, 100 mm gap and 100 mm medium successively are 4.3 °C, 1.3 °C and 1.6 °C, respectively. The two 100 mm medium zones accounts for 82.5% cooling of the total cooling effect while the 100 mm gap zone accounts for 17.5% cooling as there exists water rain in the gap zone; (2) the pressure drops of the first 100 mm medium zone, the 100 mm gap zone and the second 100 mm medium zone are 7.97 Pa, 0.31 Pa and 7.93 Pa, respectively. (3) a decrease in the cooling efficiency over 11% can be attained when the air speed changes from 0.5 m s−1 to 3.0 m s−1.