Offset Length Research Articles

Development and evaluation of a constrained optimization model for traffic signal plan transition

In advanced traffic signal control systems, plan transition is the process of switching from one timing plan to another to accommodate changes in traffic demand. In traditional coordinated system operation, whether plans are set by time of day or by traffic responsive plan selection, traffic flow can be severely disrupted by the sudden changes in traffic signal timing. Although various transition methods have been developed and refined, existing transition methods are not based on optimizing operational measures of effectiveness during plan transition periods. As the first step in remedying this situation, this paper presents a non-linear mathematical model that provides constrained delay minimization through incremental and simultaneous adjustments in offset and cycle length during plan transitions. According to the simulation results, currently used transition methods tend to assign an excessive amount of green time to the main street, resulting in additional side street delay without performance improvement for the total transportation network. By contrast, the proposed transition method showed measurable improvement in delay performance under a broad range of traffic and geometric conditions.

The Dislocator, Early and Late: The 3 am Phone Call

Hip dislocation is one of the most common causes of patient and surgeon dissatisfaction following hip replacement. To correctly treat dislocation, the causes must first be understood. Patient factors include age older than 70 years, medical comorbidities, female sex, musculoligamentous laxity, revision surgery, issues with the abductors and trochanter, and lack of education. Issues related to the surgeon and technique are surgical volume and experience, surgical approach and repair, adequate restoration of femoral offset and leg length, correct component position, and avoidance of soft tissue or bony impingement. Chief among implant-related factors is the design of the head and neck region. Is the femoral head diameter sufficient, and, in concert with the prosthetic neck, is there an adequate head-neck ratio? Skirts on longer neck lengths greatly reduce the head-neck ratio and should be avoided if possible. There must be available offset choices to restore soft tissue tension. Lipped liners aid in gaining stability, yet may result in impingement and dislocation if improperly placed. Late dislocation may result from polyethylene wear, soft tissue destruction, trochanteric or abductor disruption and weakness, or infection. Understanding the causes of hip dislocation allow prevention in a majority of instances. Proper preoperative planning includes the identification of high-offset patients in whom inadequate restoration of offset will reduce soft tissue tension and abductor efficiency. Component position must be accurate to achieve stability without impingement. Finally, patient education cannot be overemphasized, as most dislocations occur early and are preventable with proper instructions.

Are leg length and hip offset comparable after hip resurfacing and cementless total hip arthroplasty?

The purpose of this study was to determine if hip resurfacing arthroplasty (HRA) and cementless total hip arthroplasty (THA) were comparable in correcting leg length and hip offset in patients with primary osteoarthritis. A retrospective analysis was performed of 80 patients who underwent either HRA or cementless THA for primary osteoarthritis (40 in each group) between 2006 and 2008. Standardised anteroposterior radiographs taken pre-operatively and at one year following surgery were used to calculate the total offset and leg length in both hips. At one year following surgery, no leg length discrepancy was identified in either group. A difference of 0.39 cm (p=0.046) remained between the mean total offset of the operated hip and the contralateral non-operated hip in the HRA group. No difference in offset was observed between the two hips after surgery in the THA group (p=0.875). Leg length is restored by HRA and THA. A difference remains in offset after HRA although we attribute this to intentional medialisation of the acetabular cup.

The 1.4-m Telescope for the Q/U Imaging Experiment

The optical design of the 1.4-m telescope for the Q/U Imaging ExperimenT (QUIET) is described. The telescope is intended to image the polarization of the cosmic microwave background (CMB) with detectors at two frequencies (Q- and W-band) with unprecedented sensitivity. The RF optics uses a classical Dragonian side-fed geometry that employs a paraboloidal main reflector illuminated by a concave hyperboloidal subreflector. The relatively large offset distance and focal length of the main reflector, and the avoidance of caustics between the two reflectors, yield relatively flat reflectors with very low cross-polarization and a wide field of view capability. The antenna is fed by either a 91-element W-band or a 19-element Q-band corrugated platelet feed horn array. The telescope is installed on the CBI platform in Chile, and data taking is underway.

High-Performance Drain-Offset a-IGZO Thin-Film Transistors

We report the effect of the drain-offset length on the performance of amorphous-indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs). While the field-effect mobility decreases from <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex> </formula> 40 to 10 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{cm}^{2}/\hbox{V}\cdot \hbox{s}$</tex></formula> by increasing the drain-offset length from 0 to 5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> , the threshold voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(V_{\rm th})$</tex></formula> and swing <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(S)$</tex></formula> remain relatively independent of the offset length variation. Because of its high mobility even for large (5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex> </formula> ) offset lengths, the drain-offset a-IGZO TFT can be used to eliminate the kickback voltage in active-matrix displays.

A modular cementless stem vs. cemented long-stem prostheses in revision surgery of the hip

Background and purpose Modular cementless revision prostheses are being used with increasing frequency. In this paper, we review risk factors for the outcome of the Link MP stem and report implant survival compared to conventional cemented long-stem hip revision arthroplasties.Patients and methods We used data recorded in the Swedish Hip Arthroplasty Register. 812 consecutive revisions with the MP stem (mean follow-up time 3.4 years) and a control group with 1,073 cemented long stems (mean follow-up time 4.2 years) were included. Kaplan-Meier analysis was used to determine implant survival. The Cox regression model was used to study risk factors for reoperation and revision.Results The mean age at revision surgery for the MP stem was 72 (SD 11) years. Decreasing age (HR = 1.1, 95% CI: 1–1.1), multiple previous revisions (HR = 2.6, 95% CI: 1.1–6.2), short stem length (HR = 2.4, 95% CI: 1.1–5.2), standard neck offset (HR = 5, 95% CI: 1.5–17) and short head-neck length (HR = 5.3, 95% CI 1.4–21) were risk factors for reoperation. There was an overall increased risk of reoperation (HR = 1.7, 95% CI: 1.3–2.4) and revision (HR = 1.9, 95% CI: 1.2–3.1) for the MP prostheses compared to the controls.Interpretation The cumulative survival with both reoperation and revision as the endpoint was better for the cemented stems with up to 3 years of follow-up. Thereafter, the survival curves converged, mainly because of increasing incidence of revision due to loosening in the cemented group. We recommend the use of cemented long stems in patients with limited bone loss and in older patients.

ML Estimation of Timing and Frequency Offsets Using Distinctive Correlation Characteristics of OFDM Signals Over Dispersive Fading Channels

Orthogonal frequency-division multiplexing (OFDM) is a promising technology for communication systems. However, the synchronization of OFDM over dispersive fading channels remains an important and challenging issue. In this paper, a synchronization algorithm for determining the symbol timing offset and the carrier frequency offset (CFO) in OFDM systems, based on the maximum-likelihood (ML) criterion, is described. The new ML approach considers time-dispersive fading channels and employs distinctive correlation characteristics of the cyclic prefix at each sampling time. The proposed symbol timing estimation is found to be a 2-D function of the symbol timing offset and channel length. When compared with previous ML approaches, the proposed likelihood function is optimized at each sampling time without requiring additional pilot symbols. To practically realize the proposed method, a suboptimum approach to the ML estimation is adopted, and an approximate but closed-form solution is presented. Nonlinear operations of the approximate solution can be implemented using a conventional lookup table to reduce the computational complexity. The proposed CFO estimation is also found to depend on the channel length. Unlike conventional schemes, the proposed method fully utilizes the delay spread of dispersive fading channels (which usually reduces the accuracy of estimations). Furthermore, the Cramer-Rao lower bound (CRLB) on the CFO estimate is analyzed, and simulations confirm the advantages of the proposed estimator.

Digital templating in total hip arthroplasty in the NHS: ‘computer says no…’

Preoperative planning plays an important role in any surgical procedure and total hip replacement (THR) is no exception. Templating of radiographs allows preoperative assessment of the correct size of implant to be used, lowers the risk of periprosthetic fracture, helps restore femoral offset and leg length, facilitates the optimisation of alignment and ensures the correct implants sizes are available. All of these reduce the intraoperative pressures leading to the selection of incorrectly sized implants. This study assessed whether there is adequate provision of the current NHS Picture Archiving and Communication Systems (PACS) to allow optimal digital templating for THRs. Data were collected using a telephone questionnaire requesting information from the on-call orthopaedic SpR in 28 Greater London and surrounding area NHS Hospitals. PACS were used in all 28 (100%) hospitals that were contacted. Digital templating software was available in 14 (50%) hospitals. Despite this, none of them performed digital templating regularly. In the 50% that did have digital templating, this was not routinely done for the following reasons; only 3 (10.7%) allowed easy access to the software to the SpRs; only one SpR received formal training on how to use the system; only one hospital regularly used methods to accurately allow the software to assess magnification for accurate sizing (e.g. sizing balls). Digital PACS systems have made great improvements in the access of radiographs in the NHS. In orthopaedic practice, however, we have shown that the benefit of digital templating is being overlooked within the NHS.

Development and evaluation of a constrained optimization model for traffic signal plan transition

In advanced traffic signal control systems, plan transition is the process of switching from one timing plan to another to accommodate changes in traffic demand. In traditional coordinated system operation, whether plans are set by time of day or by traffic responsive plan selection, traffic flow can be severely disrupted by the sudden changes in traffic signal timing. Although various transition methods have been developed and refined, existing transition methods are not based on optimizing operational measures of effectiveness during plan transition periods. As the first step in remedying this situation, this paper presents a non-linear mathematical model that provides constrained delay minimization through incremental and simultaneous adjustments in offset and cycle length during plan transitions. According to the simulation results, currently used transition methods tend to assign an excessive amount of green time to the main street, resulting in additional side street delay without performance improvement for the total transportation network. By contrast, the proposed transition method showed measurable improvement in delay performance under a broad range of traffic and geometric conditions.

Effect of triple pelvic osteotomy on the proximal femoral geometry in dysplastic dogs

Triple pelvic osteotomy (TPO) is one of the surgical procedures for use to try to reduce subsequent degenerative joint disease or modify the progress of hip dysplasia in young dogs. Joint force and pressure distribution were changed by this procedure. Therefore, the aim of this study was to find out whether the remodeling of proximal femur exists or not after TPO in dysplastic dogs. Ten femora from five young dysplastic mongrel dogs, treated unilaterally with TPO using 20° canine pelvic osteotomy plates, were used. One year after TPO, neck-proximal shaft angle, femoral head, neck, diaphyseal and mid-shaft diameters, total femoral, femoral neck axis, and intertrochanteric, femoral head offset lengths as well as the lengths from head center to lateral margin of greater trochanter and to proximal femoral axis were measured from the bone. The significant differences between treatment and control side were determined in Norberg angle, neck-proximal shaft angle, neck diameter, diaphyseal diameter, mid-shaft diameter, length from head center to proximal femoral axis and femoral head offset length. In conclusion, although small number of cases was used, it was determined that the aforementioned variables are affected by TPO. So, these variables may be supply additional information about the changes to the joint following TPO in dysplastic dogs.

A Comparison of Two Implant Systems in Restoration of Hip Geometry in Arthroplasty

Restoration of hip offset and leg length during THA is often limited by available implant geometries. The recent introduction of femoral components with a modular junction at the base of the neck (two modular junction components) has expanded the options to restore femoral offset and leg length. We asked (1) whether a femoral component with two modular junctions would predict by templating more frequent restoration of preoperative offset and leg length abnormalities than one with single modular junctions; and (2) how our use of these options compared with national sales data. We retrospectively reviewed the preoperative templating data in 100 primary THAs using single modular junction implants with only a neutral version stem and 100 THAs using two modular junction implants. We compared the frequency with which the desired leg length and offset were completely restored by preoperative templating in the two groups. Offset and leg lengths were restored to within 1 mm in 85% of cases with two modular junction implants and 60% of cases with single modular junction implants. An anteverted or a retroverted neck was used in 25% of cases with the two modular junction stems. The national sales data revealed femoral neck components with version were used in 28% of cases. The use of a femoral component with two modular junctions resulted in more frequent ability to restore femoral offset and leg length than a single modular junction. The advantage of clinical flexibility should be tempered by the potential concerns of prosthetic mechanical failure (which has been reported in another implant system with two modular junctions), increased third-body wear and corrosive debris, and increased prosthetic cost. Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Cost and Entropy Generation Minimization of a Cross-Flow Plate Fin Heat Exchanger Using Multi-Objective Genetic Algorithm

In the present work, a thermal modeling is conducted for optimal design of compact heat exchangers in order to minimize cost and entropy generation. In this regard, an ε−NTU method is applied for estimation of the heat exchanger pressure drop, as well as effectiveness. Fin pitch, fin height, fin offset length, cold stream flow length, no-flow length, and hot stream flow length are considered as six decision variables. Fast and elitist nondominated sorting genetic algorithm (i.e., nondominated sorting genetic algorithm II) is applied to minimize the entropy generation units and the total annual cost (sum of initial investment and operating and maintenance costs) simultaneously. The results for Pareto-optimal front clearly reveal the conflict between two objective functions, the number of entropy generation units and the total annual cost. It reveals that any geometrical changes, which decrease the number of entropy generation units, lead to an increase in the total annual cost and vice versa. Moreover, for prediction of the optimal design of the plate fin heat exchanger, an equation for the number of entropy generation units versus the total annual cost is derived for the Pareto curve. In addition, optimization of heat exchangers based on considering exergy destruction revealed that irreversibilities, such as pressure drop and high temperature difference between cold and hot streams, play a key issue in exergy destruction. Thus, more efficient heat exchanger leads to have a heat exchanger with higher total cost rate. Finally, the sensitivity analysis of change in the optimum number of entropy generation units and the total annual cost with change in the decision variables of the plate fin heat exchanger is also performed, and the results are reported.

A novel fabrication process of a gate offset nonvolatile memory on glass and the influence of the gate offset structure on the device characteristics

Effective memory performance of the nonvolatile memory/thin film transistor (NVM/TFT) devices needs good TFT characteristics. The reduction in leakage current of the TFT devices was accomplished with the gate offset (GOF) structure. A simplified fabrication process for the GOF NVM is introduced in this study using the insulator over-etching approach. Nonvolatile memory devices on glass using SiO 2/SiO x /SiO x N y stack with an offset length of 0, 0.2, 0.4, and 0.6 μm were investigated. The highly selective etching process and the short offset length help to avoid the problem of the gate aluminum collapsing on the source/drain electrodes. The TFT characteristics of the GOF structures displayed the remarkable improvement in leakage from 1.1 × 10 −11 A, for the TFT without an offset region, to the low OFF current of 1.34 × 10 −12 A for the device with a 0.6 μm offset length. The longer offset length gave the lowest OFF current. The degradation in transconductance and the threshold voltage was negligible with the g m values of about 3 × 10 −6 S and Δ V th of about 0.2 V, respectively. The switching characteristics remained similar for all the devices. Additionally, the GOF structures slightly enhanced the retention characteristics. The memory window of the NVM without the offset after a retention time of 10,000 s was 58%, lower than the over 69% of the GOF devices. Therefore, the application of the GOF structure to reduce the leakage of the NVM/TFT proved to be effective.

Electrical Characteristics of a Reduced-Gate Structure Polycrystalline Silicon Thin Film Transistor Using Field-Aided Lateral Crystallization

In order to reduce the leakage current in n-channel polycrystalline silicon thin film transistors processed by field-aided lateral crystallization, we applied a reduced gate structure that enables an offset region between the channel and source-drain. The structure in this study was much simpler than those of other methods in the sense that it could accomplish both offset-gate and Ni-offset effects simultaneously without employing any additional masks or processes. The leakage current decreased as the offset region length ΔL per side increased. When ΔL = 2 μm, which corresponded to 10 percent of the total channel length of L = 20 μm, the off-state leakage current decreased to 3.2 pA/μm at VD = 0.1 V and VG = -10 V, which is more than two orders of magnitude lower than that in the conventional structure. In addition to a reduction in leakage current, other device parameters did not change significantly.

Hip offset in total hip arthroplasty: quantitative measurement with navigation.

Offset in THA correlates to abductor muscle function, wear, and impingement. Femoral offset after THA is not independent of the cup center of rotation (COR) so hip offset, a combination of femoral offset and change in hip COR, becomes the important measurement. We therefore asked whether hip offset in arthritic hips would correlate with cup COR; whether offset could always be balanced within 6 mm of contralateral normal hips; and whether hip length could also be kept within 6 mm. We compared hip offset of arthritic and contralateral normal hips on radiographs in 82 patients (82 hips) who had THA. We used computer navigation in all patients with the aim of reconstructing the hip offset and to compare hip offset change to the quantitative change of the hip COR. The preoperative radiographic change to equalize the offset ranged from -12 to +21 mm (mean, 1.5); postoperatively the change was 1.4 ± 6.4 mm and was within ± 6 mm in 78 of 82 hips. As COR displaced superiorly from 3 to 6+ mm the offset had to be substantially increased. Only with COR 0-3 mm superior and 0-5 mm medial was offset always within 5 mm. Hip offset reconstruction was directly related to the position of the hip COR, and navigation allowed quantitative control of offset and hip length.

Corrosion-Induced Fracture of a Double-Modular Hip Prosthesis

Modularity is an important aspect of total hip replacement design. A modular Morse taper is commonly used to attach the femoral head to the femoral stem. Newer double-modular designs incorporate a second interface at the neck-stem junction. Increased modularity purportedly allows the surgeon to more closely restore patient anatomy, such as limb length, lateral offset, and femoral anteversion, and to better balance the soft tissue to achieve optimal biomechanics. However, modularity also increases the number of mechanical junctions that may lead to fretting (micromotion)1, corrosion2,3, and ultimately fracture. We have evaluated a double-modular PROFEMUR Z stem (Wright Medical Technology, Arlington, Tennessee) after catastrophic failure due to a fractured neck component at the neck-stem junction. This retrieval allowed us to analyze the mechanical failure mechanisms associated with a double-modular design. We hypothesized that modularity at the neck-stem junction resulted in fretting and crevice corrosion, which led to crack initiation and, on the application of an overload event, to fracture. The patient was informed that data concerning the case would be submitted for publication, and he consented. In June 2006, a thirty-year-old man with rheumatoid arthritis who was 6 ft and 6 in (2 m) tall, weighed 242 lb (109.8 kg), and had a body mass index of 29 kg/m2 underwent an uncomplicated right total hip arthroplasty with a cementless PROFEMUR Z hip stem with a long, straight neck (no varus/valgus offset) and a ceramic-on-ceramic articulation. The ceramic-on-ceramic modular implant was considered to be indicated in this particular patient because of his young age, high body mass index, active lifestyle, and profession. A modular stem was used in an effort to reproduce the anatomic femoral anteversion, offset, and lower-limb length to optimize hip abductor and biomechanical function. The hip functioned well until April 2008, when …

CFO estimation in OFDM systems under timing and channel length uncertainties with model averaging

In this letter, we investigate the problem of CFO estimation in OFDM systems when the timing offset and channel length are not exactly known. Instead of explicitly estimating the timing offset and channel length, we employ a multi-model approach, where the timing offset and channel length can take multiple values with certain probabilities. The effect of multimodel is directly incorporated into the CFO estimator. Results show that the proposed estimator outperforms the estimator selecting only the most probable model and the method taking the maximal model.

The Optimal Metal-Metal Arthroplasty Is Not a Surface Replacement—Affirms

Although surface replacement arthroplasty (SRA) of the hip remains intuitively appealing and aggressively marketed, the data suggest that short-term and intermediate results of surface replacement are not as good as conventional total hip replacement. Significantly worse results are observed in specific age and gender categories. In addition, there are clear limitations to biomechanical aspects of SRA, such as offset and limb length restoration. SRA continues to be an evolving aspect of hip replacement technique, and should remain an investigational procedure confined to specialized centers.

Gas-Liquid Combined Multiple Cut for WEDM

This study investigates the dry WEDM in multiple cut. To improve surface quality with high-speed WEDM (HS-WEDM), a new procedure as Gas-liquid Combined Multiple Cut (roughing is processed in dielectric liquid, and semi-finishing is in liquid or gas, while the finishing is in gas) is presented. Effects of pulse duration, peak current, offset, worktable feed and wire length on roughness and removal rate for dry semi-finishing were studied were studied with L16(45) design, and significant order inflluncing roughness and removal rate were found. Experiment results show that multiple cut with dry WEDM in semi-finishing and finishing can improve surface roughness significantly.

Präoperative Planung und Rekonstruktion in der primären Hüftendoprothetik mit und ohne modularen Hals

Preoperative planning is regarded as an important requirement for successful implantation of a hip replacement. One of the crucial aspects of planning is the restoration of the normal anatomy of the hip as this increases the chances for good clinical function and reduces wear debris. Various systems for restoration of the hip are available including stem systems with different stem sizes and offsets and so-called modular stem systems which have the additional possibility of adjusting the neck length and angle. The aim of this study was to investigate to what extent a good postoperative outcome can be achieved using a modular and a non-modular stem system in comparison with preoperative planning. Furthermore, the study assessed the difference between preoperative planning carried out by a senior surgeon and by an assistant surgeon. Standard preoperative and postoperative digitalised radiographs with an anteroposterior view of the pelvis centred over the pubic symphysis were made. Preoperative planning aimed for exact reconstruction of offset and equal leg length. Preoperative planning and evaluation of the postoperative outcome were performed by digitalised image-analysing software. The symptom-free contralateral hip served as reference for anatomic reconstruction. The postoperative results confirmed the preoperative planning. The preoperative planning was successfully implemented with both systems. Postoperatively, we observed a slightly reduced offset (Group 1: 3.6 mm, Group 2: 3.54 mm) and an increase in leg length of less than 5 mm in both groups. There was no significant difference between the preoperative planning carried out by the senior surgeon and the assistant surgeon. Implementation of preoperative planning with both the modular and the non-modular system was very satisfactory. It was irrelevant if the planning was carried out by a senior surgeon or by an assistant surgeon in the first year of training.