Box-shaped Research Articles

Feasibility of Metal Testicle Shield By 3D Printing for CT Image-Based Treatment Planning

This study aims to evaluate the feasibility of metal testicle shield for 3D CT image-based treatment planning using 3D dose calculation algorithm. The testicle shield was designed in the shape of box to minimize scatter radiation to the testicles and to be available in prone position. The testicle shield have two parts; cover and case. The dimension of case was 9.5 cm (length) × 7.5 cm (width) × 5.5 cm (height) with 2.0 cm thickness. The cover has 9.5 cm (length) × 9 cm (width) with 2.0 cm thickness. The one side of case was open sector to cover the scrotum of patient. A thin layer of silicon coating on inner surface was attached to allow comfortable attachment to the patient and to shield back-scattered electron dose from the shield. Each part was fabricated using 3D printer. The material of testicle shield was titanium which is allowed for the dose calculation using Acuros XB. To avoid metal artifact for CT image, the replica of the metal shield (dummy) was fabricated with a plastic using 3D printer for CT-sim. The rectal cancer patient underwent CT scan with dummy shield. In the treatment planning system (TPS), the dummy testicle shield was contoured, and material of dummy was assigned to titanium. Three-field box (two wedged opposing beams and 3rd beam at 90° with 15 MV) technique was used for treatment plans. The dose calculation was performed using Acuros XB and AAA. The dose distributions were also calculated in EGS4/DOSXYZnrc Monte Carlo (MC) for comparison. Optically stimulated luminescent dosimeter (OSLD) was used to measure dose of inside and outside shield for evaluating shield effect. We compared between OSLD measurement, MC simulation and TPS dose calculation. The inside dose of testicle shield was reduced to 48.1% inside dose by titanium testicle shield. The dose distribution of Acuros XB have good agreement with that of MC. The average difference was 2.1% in dose voxels containing greater than 50% the normalized dose. In contrast, the average difference between AAA and MC was 23.1%. For point dose inside the shield, MC calculation agreed with the OSLD measurements within 3.0%. The difference of MC and AAA are 10% and 30% for outside and inside surface of testicle shield, respectively. The radiation shielding ability of titanium was approximately 10% lower than that of lead. When the material of testicle shield is titanium and the plastic dummy is used for CT-sim, the dose distribution can be calculated using Acuros XB accurately in TPS.

An Augmented Reality App to Learn to Interpret the Nutritional Information on Labels of Real Packaged Foods

Healthy eating habits involve controlling your diet. It is important to know how to interpret the nutritional information of the packaged foods that you consume. These packaged foods are usually processed and contain carbohydrates and fats. Monitoring carbohydrates intake is particularly important for weight-loss diets and for some pathologies such as diabetes. In this paper, we present an augmented reality app for helping interpret the nutritional information about carbohydrates in real packaged foods with the shape of boxes or cans. The app tracks the full object and guides the user in finding the surface or area of the real package where the information about carbohydrates is located using augmented reality and helps the user to interpret this information. The portions of carbohydrates (also called carb choices or carb servings) that correspond to the visualized food are shown. We carried out a study to check the effectiveness of our app regarding learning outcomes, usability, and perceived satisfaction. A total of 40 people participated in the study (20 men and 20 women). The participants were between 14 and 55 years old. The results reported that their initial knowledge about carb choices was very low. This indicates that education about nutritional information in packaged foods is needed. An analysis of the pre-knowledge and post-knowledge questionnaires showed that the users had a statistically significant increase in knowledge about carb choices using our app. Gender and age did not influence the knowledge acquired. The participants were highly satisfied with our app. In conclusion, our app and similar apps could be used to effectively learn how to interpret the nutritional information on the labels of real packaged foods and thus help users acquire healthy life habits.

Reliability sensitivity analysis of dropped object on submarine pipelines

One of the safest and the most economical methods to transfer oil and gas is pipeline system. Prediction and prevention of pipeline failures during its assessed lifecycle has considerable importance. The dropped object is one of the accidental scenarios in the failure of the submarine pipelines. In this paper, using Monte Carlo Sampling, the probability of damage to a submarine pipeline due to a box-shaped dropped object has been calculated in terms of dropped object impact frequency and energy transfer according to the DNV-RP-F107. Finally, Reliability sensitivity analysis considering random variables is carried out to determine the effect intensity of each parameter on damage probability. It is concluded that impact area and drag coefficient have the highest sensitivity and mass and add mass coefficient have the lowest sensitivity on probability of failure.

KEKUATAN BATAS LAMBUNG KAPAL DALAM MENAHAN MOMEN LENTUR VERTIKAL

On the life, the ship will constantly get the structural load caused by the external load of the internal waves and loads of the ship's load and the structure itself which then reaches the ultimate strength of the structure. This study aims to determine the strength of the boundary of the hull due to the vertical bending moment so that the ship structure can be guaranteed security. The analysis was done by using finite element method (FEM) by modeling the structure of the tanker section modified based on the shape of the girder box so that a simpler model is obtained. This calculation is done by using ANSYS 17 software. The calculation of vessel structure is simulated based on two existing models namely girder box model and modified tanker model. In the girder box model, ultimate strength is obtained at 6,311 x 108 Nmm for hogging conditions and -6.311 x 108 Nmm for sagging conditions. While on the tanker model, the ultimate strength obtained is -8.99 x 1012 Nmm for sagging conditions and 1.0277 x 1013 Nmm for hogging conditions.

Productivity evaluation method of tight sandstone reservoir based on the logging curve

Strong heterogeneity, poor pay reservoir connectivity, and complex micro-pore structure are the reasons behind the high difficulty and low accuracy in the productivity evaluation of tight sandstone gas reservoirs. This paper utilized various well logging and mud logging curve data, summarizes the typical curve type, and made use of a mathematical method to form quantitative characterization. Additionally, a logging curve evaluation method is proposed based on the test of production capacity. The total hydrocarbon curve can be divided into six types as shown by the results: box shape, half box shape, upright triangle, inverted triangle, sawtooth shape, single peak, etc. The above is closely related to the level of oil and gas in the reservoir layer. Six types of total hydrocarbon curve can be quantified by amplitude, relative centroid, relative sawtooth, variance, and the parameter value of the autocorrelation function. The box-shaped total hydrocarbon gas logging curve is full and has a large scale. The half box-shaped total hydrocarbon gas logging curve peak scale is significantly smaller than that of the reservoir thickness. The triangularly-shaped total hydrocarbon gas logging curve may either be an upright or inverted triangle. The sawtooth-shaped total hydrocarbon gas logging curve has high and low tendencies that show a number of spikes. Single peak-shaped total hydrocarbon gas logging curve is small with a single peak. There is a good relationship between the six kinds of total hydrocarbon gas logging curve and the tight sandstone gas reservoir production capacity. The high and middle gas pay layers are mainly box-shaped and triangular, whereas the lower production layer is half box-shaped, triangular, and has a zigzag pattern. However, the low gas pay layers mainly possess a sawtooth pattern, while the non-production layer is mainly single peak in shape. The comprehensive interpretation of the total hydrocarbon gas logging curve and log resistivity curve can more accurately distinguish the production capacity of tight sandstone gas reservoirs. Finally, the quantitative model is used for automatic interpretation. Through data verification and analysis, it is found that the coincidence rate of the production gas pay layer is 80.95%, whereas the coincidence rate of production capacity is 78.05%. It is proven by practice that the gas formation capacity of tight sandstone gas reservoirs can be predicted based on the logging and mud logging well curve shapes.

Numerical simulation of partially filled liquid containers with special type bottom geometry under earthquake excitation

Numerical simulation of liquid in partially filled tank of flat bottom and bottom box shape is investigated in the present paper. Previously, dynamic response of flat bottom tank has been carried out numerously, but the dynamic response of bottom box tank remains unclear. Therefor a parametric study on bottom box shape tank is carried out to understand the dynamic response of contained liquid under both harmonic excitation and real earthquake excitation. The efficacy of the present numerical model is verified by comparing the results with the published results. Galerkin’s finite element method is used to derive the modal equations of motion for sloshing. The slosh wave displacement, hydrodynamic pressure distribution and the base shear, are quantified for the bottom box shape tank. According to the dynamic analysis results larger size of bottom box significantly reduces the effective mass of liquid which keeps the container on safer side than the flat bottom container.

An accurate dynamic model for polycrystalline shape memory alloy wire actuators and sensors

Thermal shape memory alloy (SMA) wires exhibit a mechanical hysteresis of which the shape depends on both temperature and loading rate. Commercially available actuator wires typically exhibit polycrystalline behavior, which also depends on training effects. Polycrystallinity may lead to complex hysteresis loops, differing substantially from standard box shapes often employed in modeling attempts. In addition, actuation often results in loading trajectories leading through the interior of the hysteresis, making accurate modeling and control of SMA systems a highly challenging task. In this paper, we present a novel dynamic model for polycrystalline SMA actuator wires based on a modified version of the Müller–Achenbach–Seelecke model. The model permits to predict time evolution of stress and resistance of a one-dimensional SMA wire under arbitrary input strain and Joule heating profiles. The constitutive equations are developed by properly exploiting the concept of a representative single-crystal, resulting in an optimal trade-off between physical interpretation and computational efficiency. After developing constitutive model equations, experimental validation is performed by means of two case studies, given by a superelastic NiTi wire and a quasi-plastic NiTi wire, respectively. The experiments are intended to illustrate the model capabilities in predicting internal hysteresis loops, loading rate effects, as well as actuation and sensing behavior at the same time. A remarkable accuracy is observed in all of the investigated experimental scenarios, making the model particularly suitable for high-precision control and self-sensing applications.

Multi-surrogate-assisted metaheuristics for crashworthiness optimisation

This work proposes a multi-surrogate-assisted optimisation and performance investigation of several newly developed metaheuristics (MHs) for the optimisation of vehicle crashworthiness. The optimisation problem for car crashworthiness is posed to find the shape and size of a crash box while the objective function is to maximise the total energy absorption subject to a mass constraint. Two main numerical experiments are conducted. Firstly, the performance of different surrogate models along with the proposed multi-surrogate model is investigated. Secondly, several MHs are applied to tackle the proposed crashworthiness optimisation problem by employing the best obtained surrogate model. The results reveal that the proposed multi-surrogate model is the best performer. Among the several MHs used in this study, sine cosine algorithm is the best algorithm for the proposed multi-surrogate model. Based on this study, the application of the proposed multi-surrogate model is better than using one particular traditional surrogate model, especially for constrained optimisation.

Optimizing a Gravid Mosquito Resting Box to Enhance Auto-dissemination of Larvicides under Semi-field Conditions in Western Kenya

Malaria control strategies are challenged by emergence of insecticide resistance and behavioral changes of the vector. New vector management tools are required to avert control failure. The aim of this study was to optimize a mosquito resting box that act as contamination station for auto-dissemination of novel chemicals by female Anopheles gambiae to their oviposition sites. In this study, cotton fabrics (red, black, blue, white), circular & rectangular boxes of different sizes were tested for resting preference. Optimal box size and shape, aligned with most attractive colour, was dusted with red fluorescent dye (larvicide proxy). Two artificial oviposition sites were set up in a screen house, one of which was treated with Cedrol, the other had tap water only. Two to three days old bloodfed mosquitoes were used for resting preference whereas gravid females were used for auto-dissemination experiments. A high resting preference was observed in red and black fabrics (28.08 ± 3.211), (28.00 ±3.922) respectively, compared to white (4.67±0.890). Choice of colour was found to influence mosquito landing (P=0.000<0.05). With the choice of most preferred colour, the rectangular black box (45m×30m×45m) attracted high proportion (60%) of mosquitoes. The box effectively transferred dye to the resting mosquitoes and to the oviposition site, with 67% visited oviposition site, having dye on their body. These results reveal that the black rectangular box attracted adult blood-fed and gravid mosquitoes high enough showing great potential as future malaria vector control and/or sampling tool, and is recommended for further field-based evaluation.&nbsp

Experimental Investigation on OSB Webbed Laminated Bamboo Lumber Box Shaped Joists

A novel bamboo-wood box beam was introduced in this paper, which consisted of laminated bamboo lumber flanges and OSB webs. Four-point bending tests were conducted on composite beams to investigate the effects of shear span ratio and stiffeners on failure mode and strength. The results showed that the composite beams with shear span ratio less than two failed in web shear failure, but for the others, the beams failed in twist and delamination of OSB in flanges. The load carrying capacity of beams decreased with the increase of shear span ratio. However, the mechanical performance of beams can be improved moderately by the presence of stiffeners, and theultimate bearing capacity and initial stiffness was increased by 16.5% and 13.1% respectively.

Multiscale Rotated Bounding Box-Based Deep Learning Method for Detecting Ship Targets in Remote Sensing Images.

Since remote sensing images are captured from the top of the target, such as from a satellite or plane platform, ship targets can be presented at any orientation. When detecting ship targets using horizontal bounding boxes, there will be background clutter in the box. This clutter makes it harder to detect the ship and find its precise location, especially when the targets are in close proximity or staying close to the shore. To solve these problems, this paper proposes a deep learning algorithm using a multiscale rotated bounding box to detect the ship target in a complex background and obtain the location and orientation information of the ship. When labeling the oriented targets, we use the five-parameter method to ensure that the box shape is maintained rectangular. The algorithm uses a pretrained deep network to extract features and produces two divided flow paths to output the result. One flow path predicts the target class, while the other predicts the location and angle information. In the training stage, we match the prior multiscale rotated bounding boxes to the ground-truth bounding boxes to obtain the positive sample information and use it to train the deep learning model. When matching the rotated bounding boxes, we narrow down the selection scope to reduce the amount of calculation. In the testing stage, we use the trained model to predict and obtain the final result after comparing with the score threshold and nonmaximum suppression post-processing. Experiments conducted on a remote sensing dataset show that the algorithm is robust in detecting ship targets under complex conditions, such as wave clutter background, target in close proximity, ship close to the shore, and multiscale varieties. Compared to other algorithms, our algorithm not only exhibits better performance in ship detection but also obtains the precise location and orientation information of the ship.

Minimum elastic bounding box algorithm for dimension detection of 3D objects: a case of airline baggage measurement

Motivated by the interference of appendages in airline baggage dimension detection using three-dimensional (3D) point cloud, a minimum elastic bounding box (MEBB) algorithm for dimension detection of 3D objects is developed. The baggage dimension measurements using traditional bounding box method or shape fitting method can cause large measurements due to the interference of appendages. Starting from the idea of ‘enclosing’, an elastic bounding box model with the deformable surface is established. On the basis of using principal component analysis to obtain the main direction of the bounding box, the elastic rules for deformable surfaces are developed so as to produce a large elastic force when it comes into contact with the main body part and to produce a small elastic force when it comes into contact with the appendages part. The airline baggage measurement shows how to use MEBB for dimension detection, especially for the processing of isotropic density distribution, the elasticity computing and the adaptive adjustment of elasticity. Results on typical baggage samples, comparisons to other methods, and error distribution experiments with different algorithm parameters show that the authors’ method can reliably obtain the size of the main body part of the object under the interference of appendages.

Seismic Analysis of Multi-Storied Building with Shear Walls using ETABS

Shear walls are structural members used to elongate the strength of R.C.C. structures. These shear walls will be construct in each level of the structure, to form an effective box structure. Equal length shear walls are placed symmetrically on opposite sides of outer walls of the building. Shear walls are added to the building interior to provide more strength and stiffness to the building when the exterior walls cannot provide sufficient strength and stiffness. It is necessary to provide these shear walls when the tolerable span- width ratio for the floor or roof diaphragm is exceeded. The present work deals with a study on the improvement location of shear walls in symmetrical high rise building. Position of shear walls in symmetrical buildings has due considerations. In symmetrical buildings, the center of gravity and center of rigidity coincide, so that the shear walls are placed symmetrically over the outer edges or inner edges (like box shape). So, it is very necessary to find the efficient and ideal location of shear walls in symmetrical buildings to minimize the torsion effect. In this work a high rise building with different places of shear walls is considered for analysis. The multi storey building with 8 story’s is analyzed for its displacement, strength and stability using ETABS-2015 software. For the analysis of the building for seismic loading with Zone-III is considered with soil III. The analysis of the building is done by using equivalent static method and dynamic method.

Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Samples Fabricated by Selective Laser Melting

Ti-6Al-4V (wt%) alloy samples with dog-bone and box shapes respectively were fabricated by selective laser melting (SLM). The microstructures and mechanical properties of the 3D printed Ti-6Al-4V samples with and without heat treatment were characterized and tested. The microstructures of the as-fabricated dog-bone shaped samples were mainly composed of acicular α’ phase. After annealing at 700°C, the acicular α’ phase changed into an α/β lamellar structure. After solution treatment at 955°C, water quenching and aging at 550°C, the microstructure was mainly composed of primary α phase and α/β lamellar structure. The optimum heat treatment is annealing, and the mechanical properties of the annealed sample are as follows: yield strength: 1015 MPa, ultimate tensile strength (UTS): 1083 MPa and elongation to fracture: 7.9%. The microstructures of the box-shaped samples after annealing mainly consist of α phase and α/β lamellar structure. When stretched along the direction parallel to the crystal growth direction, the yield strength and UTS of the sample are 1054 and 1090 MPa，and its elongation to fracture is 6.3%. When stretched along the direction perpendicular to the crystal growth direction, the yield strength and UTS of the sample are 1019 and 1068 MPa respectively, and its elongation to fracture is 8.7%.

The Design Characteristics of Nature-inspired Buildings

The systems, processes, and organisms optimized for the evolution of nature over several hundred million years have helped designers and architects seeking improved and innovative solutions. Inspired by the shape and function of nature, some architects have created great architectures by finding and applying new design sources from nature's elements. The beautiful and mysterious nature landscape surrounding us not only gives us a new appearance for the four seasons, but also provides the source of new ideas for human. When looking at nature elements such as trees, flowers, animals, and ocean organisms, architects can find unusual perspectives, visually interesting ideas, special structures, creative details and innovative mechanisms. Most modern cities are full of buildings like the shape of supermarkets and boxes, if possible, architects should try to satisfy human emotions with beautiful scenery and natural closeness through environmental architecture. When planning for future cities and constructing new buildings, how to satisfy our yearning for a harmonious interaction with nature, and how the historic characteristics of buildings are shown to be presence. All of these are related to our fundamental human feelings and emotions, can improve holistic interrelationships between buildings and nature for human life. Nature-inspired biomimicry is a way of observing the natural world to find design solutions that may enable us to create the concepts of new building design with sustainable and healthy. This study is to analyze what are nature inspirations for the visual and conception building designs and what are the characteristic of innovative designs and technologies inspired by nature.

Evaluation of behavior of updated three-dimensional panelunder lateral load in both independent and dependent modes

Three-dimensional panels are one of the modern construction systems which can be placed in the category of industrial buildings. There have always been a lot of studies and efforts to identify the behavior of these panels and improve their capacity due to their earthquake resistance and high speed of performance. This study will provide a comparative evaluation of behavior of updated three-dimensional panel\'s structural components under lateral load in both independent and dependent modes. In fact, this study tries to simultaneously evaluate strengthening effect of three-dimensional panels and the effects of system state (independent, L-shaped and BOX shaped Walls) with reinforcement armatures with different angles on the three-dimensional panels. Overall, six independent wall model, L-shaped, roofed L-shaped, BOX-shaped walls with symmetric loading, BOX -shaped wall with asymmetrical loading and roofed BOX-shaped wall were built. Then the models are strengthened without strengthened reinforcement and with strengthened reinforcements with an angle of 30, 45 and 60 degrees. The applied lateral loading, is exerted by changing the location on the end wall. In BOX-shaped wall, in symmetric and asymmetric loading, the load bearing capacity will be increased about 200 and 50% respectively. Now, if strengthened, the load bearing capacity in symmetric and asymmetric loading will be increased 3.5 and 2 times respectively. The effective angle of placement of strengthened reinforcement in the independent wall is 45 and 60 degrees. But in BOX-shaped and L-shaped walls, the use of strengthened reinforcement 45 degrees is recommended.

Diffusion of Proteins and Lipids in Membranes Corrected for Finite-Size Effects

Translational diffusion coefficients are primary reporters on the dynamics in lipid membranes. However, diffusion coefficients of lipids and membrane proteins calculated in molecular dynamics (MD) simulations suffer from severe finite-size effects. We show that these finite-size effects can be quantified in terms of hydrodynamic theory and develop accurate correction formulas. Using large-scale coarse-grained MD simulations of up to 132 million particles, we assess the effects of box size and shape on translational diffusion in lipid membrane simulations. For the flat periodic boxes commonly used for membrane simulations, we find that the diffusion coefficients of lipids and membrane proteins increase logarithmically (and therefore without bound) with the box width. Only if the box size is increased also normal to the membrane surface, the diffusion coefficient converges. This dependence on both the size and the shape of the simulation box is captured quantitatively by a hydrodynamic theory. The corresponding correction formulas make it possible to perform meaningful comparisons of diffusion coefficients from simulations with different box sizes, and facilitate the comparison to experiment.

On the mechanical stability of the body-centered cubic phase and the emergence of a metastable cI16 phase in classical hard sphere solids.

The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures. The other three structures do not exhibit crystalline order but are characterized by common patterns in the radial distribution function and bond-orientational order parameter distribution; we refer to them as bcc-di, with i ranging from 1 to 3. We found similar outcomes when employing any of the three single occupancy cell (SOC) restrictions commonly used in the literature. We also ran long constant-pressure simulations with box shape fluctuations initiated from bcc and cI16 initial configurations. At lower pressures, all the systems evolved to defective face-centered cubic (fcc) or hexagonal close-packed (hcp) structures. At higher pressures, most of the systems initiated as bcc evolved to cI16 with some evolving to defective fcc/hcp. High pressure systems initiated from cI16 remained in that structure. We computed the chemical potential of cI16 using the Einstein crystal reference method and found that it is higher than that of fcc by ∼0.5kT-2.5kT over the pressure range studied, with the difference increasing with pressure. We find that the undistorted bcc solid, even with constant-volume and SOC restrictions applied, is so mechanically unstable that it is unsuitable for consideration as a metastable phase or as a reference system for studying bcc phases of other systems. On the other hand, cI16 is a mechanically stable structure that can spontaneously emerge from a bcc starting point but it is thermodynamically metastable relative to fcc or hcp.

First-principles study on transport property of molecular} device with non-collinear electrodes

Molecular device is the ultimate electronic devices in the view point sense of scale size.Electron transport in molecular device shows obvious quantum effect,and the transport property of molecular device will be strongly affected by the chemical and structural details,including the contact position and method between the molecule and electrodes,the angle between two electrodes connecting to the molecule.However,we notice that in the existing reports on device simulations from first principles the two electrodes are always in a collinear case.Even for multi-electrode simulations,one usually used to adopt orthogonal electrodes,namely,each pair of the electrodes is in a collinear case.As the electrode configuration will clearly affect the transport property of a device on a nanometer scale,the first principles quantum transport studies with non-collinear electrodes are of great importance,but have not been reported yet.In this paper,we demonstrate the calculations of a transport system with non-collinear electrodes based on the state-of-the-art theoretical approach where the density functional theory (DFT) is combined with the Keldysh non-equilibrium Green's function (NEGF) formalism. Technically,to model a quantum transport system with non-collinear electrodes,the center scattering region of the transport system is placed into an orthogonal simulation box in all the other quantum transport simulations,while one or two electrodes are simulated within a non-orthogonal box.This small change in the shape of the simulation box of the electrode provides flexibility to calculate transport system with non-collinear electrodes,but also increases the complexity of the background coding.To date,the simulation of transport system with non-collinear electrodes has been realized only in the Nanodcal software package. Here,we take the Au-benzene (mercaptan)-Au molecular devices for example,and systematically calculate the quantum transport properties of the molecular devices with various contact positions and methods,and specifically,we first demonstrate the effect of the angle between the two electrodes on the transport property of molecular device from first principles.In our NEGF-DFT calculations performed by Nanodcal software package,the double- polarized atomic orbital basis is used to expand the physical quantities,and the exchange-correlation is treated in the local density approximation,and atomic core is determined by the standard norm conserving nonlocal pseudo-potential.Simulation results show that the chemical and structural details not only quantitatively affect the current value of the molecular device,but also bring new transport features to a device,such as negative differential resistance.From these results,we can conclude that the physics of a transport system having been investigated in more detail and a larger parameter space such as the effect of the contact model having been assessed by a comparison with ideal contacts,further understanding of the transport system can be made and more interesting physical property of the device can be obtained,which will be useful in designing of emerging electronics.

Low incidence of adjacent segment disease after posterior lumbar interbody fusion with minimum disc distraction: A preliminary report.

Study Design:A retrospective review of prospectively collected data.Objective:To investigate the incidence of radiographic and symptomatic adjacent segment disease (ASD) and identify possible risk factors for ASD after posterior lumbar interbody fusion (PLIF) with minimum disc distraction by selecting low-height interbody cages.Summary of Background Data:Excessive disc space distraction is reportedly 1 of the risk factors for ASD after PLIF; however, the incidence and other risk factors of ASD after PLIF with minimum disc distraction remain unclear.Methods:Forty-one consecutive patients who underwent PLIF at L4-L5 and were postoperatively followed up for a minimum of 2 years were included. The height and shape (box or bullet shape) of interbody cages was determined according to the disc height and morphology of the intervertebral space assessed on preoperative computed tomography scans to avoid excessive distraction. The incidence of radiographic and symptomatic ASD was evaluated and all demographic and radiographic parameters were compared between patients with and without ASD. Multivariate logistic regression analysis was performed to identify risk factors for ASD among the variables with P < .20 in univariate analysis.Results:The overall incidence of ASD was 12.2% (5/41 patients): radiographic ASD, 7.3% (3 patients); symptomatic ASD, 4.9% (2 patients). Multivariate analysis revealed preoperative retrolisthesis of L3 on extension as the sole risk factor for ASD after PLIF with minimum disc distraction (odds ratio, 2.13; 95% confidence interval, 1.00–4.05; P = .049).Conclusions:The incidence of ASD in this study was lower than that of ASD in our previous study about PLIF with distraction of disc space (12.2% vs. 31.8%). Minimum disc distraction by selection of low-height interbody cages is a simple and effective method to prevent ASD at the surgeons’ discretion, although preexisting retrolisthesis at the adjacent upper segment should be taken into consideration.